U.S. patent application number 14/910731 was filed with the patent office on 2016-07-07 for internal combustion engine.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Hiroyuki HAGA, Yuji MIYOSHI.
Application Number | 20160194984 14/910731 |
Document ID | / |
Family ID | 51626074 |
Filed Date | 2016-07-07 |
United States Patent
Application |
20160194984 |
Kind Code |
A1 |
HAGA; Hiroyuki ; et
al. |
July 7, 2016 |
INTERNAL COMBUSTION ENGINE
Abstract
An internal combustion engine includes an exhaust valve, a
plurality of cams Ca, Cb, and Cc used to drive the exhaust valve, a
cam-switching variable valve mechanism that selects a use cam used
to drive the exhaust valve out of the plurality of cams Ca, Cb, and
Cc, and an electronic control unit that determines whether
switching abnormality of the use cam in the variable valve
mechanism is present on the basis of a locus M in a predetermined
period K which is a period in which the exhaust valve is opened.
The locus M is a locus of an in-cylinder pressure changing rate
dPc/d.theta. and is specifically a locus indicating a variation of
the in-cylinder pressure changing rate dPc/d.theta. depending on a
crank angle .theta..
Inventors: |
HAGA; Hiroyuki; (Numazu-shi,
JP) ; MIYOSHI; Yuji; (Susono-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA |
Aichi-ken |
|
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi, Aichi-ken
JP
|
Family ID: |
51626074 |
Appl. No.: |
14/910731 |
Filed: |
August 6, 2014 |
PCT Filed: |
August 6, 2014 |
PCT NO: |
PCT/IB2014/001474 |
371 Date: |
February 8, 2016 |
Current U.S.
Class: |
123/90.16 |
Current CPC
Class: |
F01L 1/20 20130101; F01L
1/267 20130101; F01L 2800/11 20130101; F02D 41/221 20130101; F01L
31/16 20130101; Y02T 10/40 20130101; F02D 35/023 20130101; F02D
2041/001 20130101 |
International
Class: |
F01L 1/20 20060101
F01L001/20; F01L 31/16 20060101 F01L031/16 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 9, 2013 |
JP |
2013-166672 |
Claims
1. An internal combustion engine comprising: a variable valve
mechanism including a plurality of cams used to drive an exhaust
valve; and an electronic control unit configured to (a) select a
use cam, which is a cam used to drive the exhaust valve, out of the
plurality of cams, and (b) determine whether switching abnormality
of the use cam is present on the basis of a locus of an in-cylinder
pressure changing rate in a predetermined period, the predetermined
period being a period in which the exhaust valve is opened.
2. The internal combustion engine according to claim 1, wherein the
variable valve mechanism is configured to switch the cams such that
a plurality of modes are performed, and the electronic control unit
is configured to set the predetermined period to at least one
period of a period in which the exhaust valve is opened by
switching of the use cam and a period in which the exhaust valve is
not opened by the switching of the use cam, when the switching of
the use cam is normally performed depending on the modes.
3. The internal combustion engine according to claim 2, wherein the
electronic control unit is configured to determine whether the
switching abnormality is present on the basis of a predetermined
item of the locus, and the predetermined item includes at least one
of (i) presence of an inflection point obtained by operating of the
exhaust valve, (ii) absence of the inflection point, (iii) value of
the inflection point, and (iv) generating timing of the inflection
point.
4. The internal combustion engine according to claim 2, wherein the
predetermined period is a period after the switching to the use cam
has started.
5. The internal combustion engine according to claim 2, wherein the
electronic control unit is configured to determine that the
variable valve mechanism is abnormal when the electronic control
unit determines that the switching abnormality is present in at
least one of the plurality of modes, and the electronic control
unit is configured to determine that the variable valve mechanism
is normal when the electronic control unit determines that the
switching abnormality is not present in all of the plurality of
modes.
6. The internal combustion engine according to claim 2, wherein the
variable valve mechanism individually fluctuates depending on cam
profiles of the plurality of cams, the variable valve mechanism
includes a plurality of fluctuation portions configured to relay
dynamic power transmitted from a cam shaft to the exhaust valve,
the cam shaft is provided with the plurality of cams, and a
plurality of coupling mechanisms configured to connect and
disconnect two fluctuation portions out of the plurality of
fluctuation portions, and the electronic control unit is configured
to select the cam used to drive the exhaust valve out of at least
three cams as the plurality of cams.
7. The internal combustion engine according to claim 6, wherein the
plurality of cams includes a first cam, a second cam, and a third
cam, the plurality of fluctuation portions include a first
fluctuation portion configured to fluctuate using the first cam, a
second fluctuation portion configured to fluctuate using the second
cam, and a third fluctuation portion configured to fluctuate using
the third cam, the plurality of coupling mechanisms includes a
first coupling mechanism and a second coupling mechanism, the first
coupling mechanism includes a first lock member that connects and
disconnects the first fluctuation portion and the second
fluctuation portion, the second coupling mechanism includes a
second lock member that connects and disconnects the second
fluctuation portion and the third fluctuation portion, the second
fluctuation portion is provided with a valve driving portion
configured to transmit dynamic power to the exhaust valve, a valve
opening period of the exhaust valve using the first cam includes a
valve opening period of the exhaust valve using the second cam, the
cam profile of the first cam and the cam profile of the second cam
are set so that an amount of lift of the exhaust valve using the
first cam is greater than an amount of lift of the exhaust valve
using the second cam, the cam profile of the third cam is set so as
to drive the exhaust valve at timing different from one of the cam
profile of the first cam and the cam profile of the second cam, and
the total number of modes is six.
8. The internal combustion engine according to claim 7, wherein the
electronic control unit is configured to determine whether
abnormality of coupling or decoupling performed by at least one of
the first lock member and the second lock member is present.
9. The internal combustion engine according to claim 2, wherein the
electronic control unit is configured to determine an abnormality
form of the switching abnormality of the use cam on the basis of
the mode and the locus in the predetermined period.
10. The internal combustion engine according to claim 7, wherein
the electronic control unit is configured to determine an
abnormality form of the switching abnormality of the use cam in the
variable valve mechanism on the basis of the mode and the locus in
the predetermined period, the modes include a first mode, the first
mode is a mode in which a switching form of the use cam is
switching from the second cam to the first cam, and the electronic
control unit is configured to determine the abnormality form on the
basis of the mode and a first inflection point when the mode is the
first mode, and the first inflection point is an inflection point
obtained with the operation of the exhaust valve using at least one
of the first cam and the second cam in the locus.
11. The internal combustion engine according to claim 10, wherein
the modes include a second mode, the second mode is a mode in which
the switching form of the use cam switches from the second cam to
the first and third cams, and the electronic control unit is
configured to determine the abnormality form on the basis of the
mode and a second inflection point when the mode is the second
mode, and the second inflection point is an inflection point
obtained with the operation of the exhaust valve using the third
cam in the locus.
12. The internal combustion engine according to claim 11, wherein
the modes include a third mode, the third mode is a mode in which
the switching form of the use cam switches from the second and
third cams to the first cam, and when the mode is the third mode,
the electronic control unit is configured to (A) determine the
abnormality form on the basis of the mode and the first inflection
point, and (B) determine the abnormality form on the basis of the
mode and the second inflection point.
13. The internal combustion engine according to claim 12, wherein a
first predetermined inflection point is an inflection point
obtained with the operation of the exhaust valve using the first
cam when the exhaust valve is driven along the cam profile of the
first cam in the locus, a deviation is a magnitude of a phase
difference between the first inflection point and the first
predetermined inflection point, the electronic control unit is
configured to determine that the abnormality form is a response
delay of switching timing of the use cam generated between the
first coupling mechanism and the second coupling mechanism when the
mode is the third mode, the first inflection point and the second
inflection point are present in the locus, and the deviation is
less than a predetermined value.
14. The internal combustion engine according to claim 13, wherein
the exhaust valve, the plurality of cams, the plurality of
fluctuation portions, and the plurality of coupling mechanisms are
provided to each of a plurality of cylinders, the electronic
control unit is configured to determine that the abnormality form
is a response delay of a switching timing of the use cam caused
between the plurality of cylinders, when the mode is the first mode
and one of a value and a phase of the first inflection point is
different more than a predetermined degree between one cylinder and
another cylinder of the plurality of cylinders, the electronic
control unit is configured to determine that the abnormality form
is a response delay of a switching timing of the use cam caused
between the plurality of cylinders, when the mode is the second
mode and the presence or absence of the second inflection point is
different between one cylinder and another cylinder of the
plurality of cylinders, and the electronic control unit is
configured to determine that the abnormality form is a response
delay of a switching timing of the use cam caused between the
plurality of cylinders, when the mode is the third mode and one of
following conditions is satisfied; (I) one of the value and the
phase of the first inflection point is different more than a
predetermined degree between one cylinder and another cylinder of
the plurality of cylinders, and (II) the presence or absence of the
second inflection point is different between one cylinder and
another cylinder of the plurality of cylinders.
15. The internal combustion engine according to claim 2, wherein
the electronic control unit is configured to repeatedly determine
whether the switching abnormality is present when determining
whether the switching abnormality is present, the electronic
control unit is configured to determine that the switching
abnormality is present when the electronic control unit repeatedly
determines for a predetermined time that the switching abnormality
is present, and the electronic control unit is configured to
determine that the switching abnormality is not present when the
electronic control unit determines that the switching abnormality
is not present before repeatedly determining that the switching
abnormality is present for the predetermined time.
16. The internal combustion engine according to claim 10, wherein
the electronic control unit is configured to control a fail-safe
control on the basis of the determined abnormality form, and the
fail-safe control includes at least one of limiting of a maximum
vehicle speed, limiting of a maximum rotation speed, and limiting
of an amount of fuel injected.
17. The internal combustion engine according to claim 2, wherein
the mode differs depending on a switching form of the use cam, and
the switching form is a form of switching from one use pattern to
the other use pattern between two use patterns of a plurality of
use patterns of the use cam.
18. The internal combustion engine according to claim 1, wherein
the electronic control unit is configured to give a warning when
the electronic control unit determines that the switching
abnormality is present.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a national phase application of
International Application No. PCT/IB2014/001474, filed Aug. 6,
2014, and claims the priority of Japanese Application No.
2013-166672, filed Aug. 9, 2013, the content of both of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an internal combustion
engine.
[0004] 2. Description of Related Art
[0005] An internal combustion engine is known which includes a
cam-switching variable valve mechanism that selects a use cam to be
used to drive an exhaust valve out of plural cams. In such an
internal combustion engine, a diagnosis device that diagnoses
whether cam switching is normally performed is disclosed in
Japanese Patent Application Publication No. 7-233742 (JP 7-233742
A). Japanese Patent Application Publication No. 1-110817 (JP
1-110817 A) discloses a valve control device of a multi-cylinder
engine that controls cam switching means of another cylinder so as
to arrange a use cam of the different cylinder as a use cam of a
defective cylinder not using a predetermined cam.
SUMMARY OF THE INVENTION
[0006] In the internal combustion engine including a cam-switching
variable valve mechanism, when switching of a use cam is not
normally performed, there is multiple reasons. Accordingly, in such
an internal combustion engine, by only determining whether
switching of the use cam is normally performed, it may not be
possible to appropriately cope with situations where switching of a
use cam is not normally performed.
[0007] The present invention provides an internal combustion engine
that can determine whether switching abnormality of a use cam is
present and that can cope with situations where the switching of a
use cam is not normally performed.
[0008] An aspect of the present invention relates to an internal
combustion engine. The internal combustion engine includes a
variable valve mechanism including plural cams used to drive an
exhaust valve and an electronic control unit (ECU). The ECU is
configured to (a) select a use cam, which is a cam used to drive
the exhaust valve, out of the plural cams, and (b) determine
whether switching abnormality of the use cam is present on the
basis of a locus of an in-cylinder pressure changing rate in a
predetermined period, and the predetermined period is a period in
which the exhaust valve is opened.
[0009] In the aspect, the variable valve mechanism may be
configured to switch the cams such that a plurality of modes are
performed. The ECU may be configured to set the predetermined
period to at least one period of a period in which the exhaust
valve is opened by switching of the use cam and a period in which
the exhaust valve is not opened by the switching of the use cam,
when the switching of the use cam is normally performed depending
on the modes.
[0010] In the aspect, the ECU may be configured to determine
whether the switching abnormality is present on the basis of a
predetermined item of the locus. The predetermined item may include
at least one of (a) presence of an inflection point obtained by
operating of the exhaust valve, (b) absence of the inflection
point, (c) value of the inflection point, and (d) generating timing
of the inflection point.
[0011] In the aspect, the predetermined period may be a period
after the switching to the use cam has started.
[0012] In the aspect, the ECU may be configured to determine that
the variable valve mechanism is abnormal when the ECU determines
that the switching abnormality is present in at least one of the
plural modes. The ECU may determine that the variable valve
mechanism is normal when the ECU determines that the switching
abnormality is not present in all of the plural modes.
[0013] In the aspect, the variable valve mechanism may individually
fluctuate depending on cam profiles of the plurality of cams. The
variable valve mechanism may include a plurality of fluctuation
portions configured to relay dynamic power transmitted from a cam
shaft to the exhaust valve, the cam shaft is provided with the
plurality of cams, and a plurality of coupling mechanisms
configured to connect and disconnect two fluctuation portions out
of the plural fluctuation portions. The ECU may be configured to
select the cam used to drive the exhaust valve out of at least
three cams as the plural cams.
[0014] In the aspect, the plural cams may include a first cam, a
second cam, and a third cam. The plurality of fluctuation portions
may include a first fluctuation portion configured to fluctuate
using the first cam, a second fluctuation portion configured to
fluctuate using the second cam, and a third fluctuation portion
configured to fluctuate using the third cam. The plural coupling
mechanisms may include a first coupling mechanism and a second
coupling mechanism. The first coupling mechanism may include a
first lock member that connects and disconnects the first
fluctuation portion and the second fluctuation portion. The second
coupling mechanism may include a second lock member that connects
and disconnects the second fluctuation portion and the third
fluctuation portion. The second fluctuation portion may be provided
with a valve driving portion configured to transmit dynamic power
to the exhaust valve. A valve opening period of the exhaust valve
using the first cam may include a valve opening period of the
exhaust valve using the second cam. The cam profile of the first
cam and the cam profile of the second cam may be set so that an
amount of lift of the exhaust valve using the first cam is greater
than an amount of lift of the exhaust valve using the second cam.
The cam profile of the third cam may be set so as to drive the
exhaust valve at timing different from one of the cam profile of
the first cam and the cam profile of the second cam. The total
number of modes may be six.
[0015] In the aspect, the ECU may be configured to determine
whether abnormality of coupling or decoupling performed by at least
one of the first lock member and the second lock member is
present.
[0016] In the aspect, the ECU may be configured to determine an
abnormality form of the switching abnormality of the use cam on the
basis of the mode and the locus in the predetermined period.
[0017] In the aspect, the ECU may be configured to determine an
abnormality form of the switching abnormality of the use cam in the
variable valve mechanism on the basis of the mode and the locus in
the predetermined period. The modes may include a first mode, and
the first mode may be a mode in which a switching form of the use
cam is switching from the second cam to the first cam. The ECU may
be configured to determine the abnormality form on the basis of the
mode and a first inflection point when the mode is the first mode.
The first inflection point may be an inflection point obtained with
the operation of the exhaust valve using at least one of the first
cam and second cam in the locus.
[0018] In the aspect, the modes may include a second mode, and the
second mode may be a mode in which the switching form of the use
cam is switching from the second cam to the first and third cams.
The ECU may be configured to determine the abnormality form on the
basis of the mode and a second inflection point when the mode is
the second mode, and the second inflection point may be an
inflection point obtained with the operation of the exhaust valve
using the third cam in the locus.
[0019] In the aspect, the modes may include a third mode, and the
third mode may be a mode in which the switching form of the use cam
is switching from the second and third cams to the first cam. When
the mode is the third mode, the ECU may be configured to (a)
determine the abnormality form on the basis of the mode and the
first inflection point, and (b) determine the abnormality form on
the basis of the mode and the second inflection point.
[0020] In the aspect, a first predetermined inflection point may be
an inflection point obtained with the operation of the exhaust
valve using the first cam when the exhaust valve is driven along
the cam profile of the first cam in the locus. A deviation may be a
magnitude of a phase difference between the first inflection point
and the first predetermined inflection point. The ECU may determine
that the abnormality form is a response delay of switching timing
of the use cam generated between the first coupling mechanism and
the second coupling mechanism when the mode is the third mode, the
first inflection point and the second inflection point are present
in the locus, and the first inflection point is an inflection point
of which a deviation is less than a predetermined value.
[0021] In the aspect, the exhaust valve, the plural cams, the
plural fluctuation portions, and the plural coupling mechanisms may
be provided to each of plural cylinders. The ECU may be configured
to determine that the abnormality form is a response delay of a
switching timing of the use cam caused between the plural cylinders
when the mode is the first mode and the value or phase of the first
inflection point is different more than a predetermined degree
between one cylinder and another cylinder of the plural cylinders.
The ECU may be configured to determine that the abnormality form is
a response delay of a switching timing of the use cam caused
between the plural cylinders when the mode is the second mode and
the presence or absence of the second inflection point is different
between one cylinder and another cylinder of the plural cylinders.
The electronic control unit may be configured to determine that the
abnormality form is a response delay of a switching timing of the
use cam caused between the plurality of cylinders, when the mode is
the third mode and one of following conditions is satisfied. One of
the conditions are that one of the value and the phase of the first
inflection point is different more than a predetermined degree
between one cylinder and another cylinder of the plurality of
cylinders. The other of conditions is that the presence or absence
of the second inflection point is different between one cylinder
and another cylinder of the plurality of cylinders.
[0022] In the aspect, the ECU may be configured to repeatedly
determine whether the switching abnormality is present when
determining whether the switching abnormality is present. The ECU
may be configured to determine that the switching abnormality is
present when the ECU repeatedly determines for a predetermined time
that the switching abnormality is present. The ECU may be
configured to determine that the switching abnormality is not
present when the ECU determines that the switching abnormality is
not present before repeatedly determining that the switching
abnormality is present for the predetermined time.
[0023] In the aspect, the ECU may be configured to control a
fail-safe control on the basis of the determined abnormality form.
The fail-safe control may include at least one of limiting of a
maximum vehicle speed, limiting of a maximum rotation speed, and
limiting of an amount of fuel injected.
[0024] In the aspect, the modes may differ depending on a switching
form of the use cam, and the switching form may be a form of
switching from one use pattern to the other use pattern between two
use patterns of plural use patterns of the use cam.
[0025] In the aspect, the ECU may be configured to give a warning
when the ECU determines that the switching abnormality is
present.
[0026] According to the aspect, it is possible to determine whether
switching abnormality of a use cam is present and to appropriately
cope with situations where the switching of a use cam is not
normally performed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Features, advantages, and technical and industrial
significance of exemplary embodiments of the invention will be
described below with reference to the accompanying drawings, in
which like numerals denote like elements, and wherein:
[0028] FIG. 1 is a diagram illustrating an overall configuration of
an internal combustion engine and peripheries thereof;
[0029] FIG. 2 is a diagram schematically illustrating a
configuration of the internal combustion engine;
[0030] FIG. 3 is a diagram illustrating a cam shaft;
[0031] FIG. 4 is a first outside view of a variable valve
mechanism;
[0032] FIG. 5 is a second outside view of the variable valve
mechanism;
[0033] FIG. 6 is a side view of the variable valve mechanism;
[0034] FIG. 7 is a diagram schematically illustrating a
configuration of a unit;
[0035] FIG. 8 is a diagram illustrating plural coupling
mechanisms;
[0036] FIGS. 9A to 9C are diagrams illustrating use patterns of use
cams;
[0037] FIG. 10 is a diagram illustrating a predetermined
period;
[0038] FIG. 11A and FIG. 11B are a flowchart illustrating an
example of an entire control;
[0039] FIGS. 12A to 12F are diagrams illustrating first mechanical
failure in a first mode;
[0040] FIGS. 13A to 13F are diagrams illustrating second mechanical
failure in the first mode;
[0041] FIGS. 14A to 14F are diagrams illustrating third mechanical
failure in the first mode;
[0042] FIG. 15 is a first flowchart illustrating a first control
example;
[0043] FIG. 16 is a second flowchart illustrating the first control
example;
[0044] FIG. 17 is a third flowchart illustrating the first control
example;
[0045] FIG. 18 is a fourth flowchart illustrating the first control
example;
[0046] FIGS. 19A to 19F are diagrams illustrating first mechanical
failure in a second mode;
[0047] FIGS. 20A to 20F are diagrams illustrating second mechanical
failure in the second mode;
[0048] FIGS. 21A to 21F are diagrams illustrating third mechanical
failure in the second mode;
[0049] FIG. 22 is a first flowchart illustrating a second control
example;
[0050] FIG. 23 is a second flowchart illustrating the second
control example;
[0051] FIG. 24 is a third flowchart illustrating the second control
example;
[0052] FIG. 25 is a fourth flowchart illustrating the second
control example;
[0053] FIGS. 26A to 26I are diagrams illustrating mechanical
failure in a third mode;
[0054] FIGS. 27A to 27C are diagrams illustrating first
responsiveness failure;
[0055] FIG. 28A and FIG. 28B are a first flowchart illustrating a
third control example;
[0056] FIG. 29 is a second flowchart illustrating the third control
example;
[0057] FIG. 30 is a third flowchart illustrating the third control
example;
[0058] FIG. 31 is a diagram illustrating second responsiveness
failure;
[0059] FIG. 32 is a first flowchart illustrating a fourth control
example; and
[0060] FIG. 33 is a second flowchart illustrating the fourth
control example.
DETAILED DESCRIPTION OF EMBODIMENTS
[0061] FIG. 1 is a diagram illustrating an overall configuration of
an internal combustion engine 50 and peripheries thereof. FIG. 2 is
a diagram schematically illustrating a configuration of the
internal combustion engine 50. FIGS. 3A and 3B are diagrams
illustrating a cam shaft 65. FIG. 4 is a first outside view of a
variable valve mechanism 60. FIG. 5 is a second outside view of the
variable valve mechanism 60. FIG. 6 is a side view of the variable
valve mechanism 60. FIG. 3A is a diagram illustrating the entire
configuration of the cam shaft 65 and FIG. 3B is a cross-sectional
view of cams Ca, Cb, and Cc taken along line A-A of FIG. 3A. FIGS.
5 and 6 illustrate the variable valve mechanism 60 along with the
cam shaft 65.
[0062] The internal combustion engine 50 is provided with an intake
system 10, an exhaust system 20, and an exhaust recirculation
system 40. The intake system 10 includes an air flowmeter 11, an
intercooler 12, and an intake manifold 13. The air flowmeter 11
measures an amount of intake air. The intercooler 12 cools the
intake air. The intake manifold 13 distributes the intake air to
cylinders 51a of the internal combustion engine 50. The exhaust
system 20 includes an exhaust manifold 21 and a catalyst 22. The
exhaust manifold 21 merges exhaust air from the cylinders 51a into
one exhaust passage on the downstream side. The catalyst 22
purifies the exhaust air. The intake system 10 and the exhaust
system 20 are provided with a supercharger 30. The supercharger 30
supercharges the internal combustion engine 50 with the intake
air.
[0063] The exhaust recirculation system 40 includes an EGR pipe 41,
an EGR cooler 42, and an EGR valve 43. The EGR pipe 41 causes the
intake system 10 and the exhaust system 20 to communicate with each
other. Specifically, the EGR pipe 41 causes a merging portion on
the upstream side of the intake manifold 13 and a merging portion
on the downstream side of the exhaust manifold 21 to communicate
with each other. The EGR cooler 42 cools the recirculated exhaust
air. The EGR valve 43 adjusts an amount of exhaust air
recirculated. The internal combustion engine 50 is a
compression-ignited internal combustion engine and includes plural
cylinders (four herein) cylinders 51a. The internal combustion
engine 50 along with the intake system 10, the exhaust system 20,
and the exhaust recirculation system 40 is mounted on a vehicle not
illustrated.
[0064] The internal combustion engine 50 includes an electronic
control unit (ECU) 70. The internal combustion engine 50 includes a
cylinder block 51, a cylinder head 52, a piston 53, an intake valve
54, an exhaust valve 55, a fuel injection valve 56, a variable
valve mechanism 60, and a cam shaft 65. The internal combustion
engine 50 is provided with an in-cylinder pressure sensor 91. The
piston 53, the intake valve 54, the exhaust valve 55, the fuel
injection valve 56, and the in-cylinder pressure sensor 91 are
provided to each cylinder 51a.
[0065] The cylinder 51a is formed in the cylinder block 51. The
piston 53 is housed in the cylinder 51a. The cylinder head 52 is
fixed to the top surface of the cylinder block 51. A combustion
chamber E is formed as a space surrounded with the cylinder block
51, the cylinder head 52, and the piston 53. The piston 53 is
adjacent to the combustion chamber E.
[0066] An intake port 52a guiding intake air to the combustion
chamber E and an exhaust port 52b exhausting gas from the
combustion chamber E are formed in the cylinder head 52. The
cylinder head 52 is provided with the intake valve 54 switching the
intake port 52a and the exhaust valve 55 switching the exhaust port
52b. The number of intake valves 54 and the number of exhaust
valves 55 provided to each cylinder 51a are two or more (two
herein). The fuel injection valve 56 is disposed in the cylinder
head 52 and injects fuel to the combustion chamber E. The
in-cylinder pressure sensor 91 is disposed in the cylinder head 52
and senses an in-cylinder pressure Pc which is the pressure of the
combustion chamber E.
[0067] The variable valve mechanism 60 is disposed in the cylinder
head 52. The variable valve mechanism 60 is a cam-switching
variable valve mechanism and selects a use cam to be used to drive
the exhaust valve 55 out of a cam Ca as a first cam, a cam Cb as a
second cam, and a cam Cc as a third cam. The cams Ca, Cb, and Cc
are disposed in the cam shaft 65 and constitute plural (three
herein) cams used to drive the exhaust valve 55. The number of cams
may be set to at least three.
[0068] The cams Ca, Cb, and Cc have different cam profiles
different from each other. The cam profiles of the cams Ca, Cb are
set so as to drive the exhaust valve 55 with at least one (an
exhaust stroke herein) of an exhaust stroke and an intake stroke.
The cam profiles of the cams Ca, Cb are set so that a valve opening
period of the exhaust valve 55 using the cam Cb is included in a
valve opening period of the exhaust valve 55 using the cam Ca and
an amount of lift of the exhaust valve 55 using the cam Ca is
greater than an amount of lift of the exhaust valve 55 using the
cam Cb.
[0069] The cam profile of the cam Cc is set so as to drive the
exhaust valve 55 at a timing different from one of the cam profile
of the cam Ca and the cam profile of the cam Cb. The cam profile of
the cam Cc is specifically set to open the exhaust valve 55 in a
valve opening period of the intake valve 54. The cam Cc is used
along with the cam Cb. The cam Cc may be used along with the cam
Ca.
[0070] The cams Ca, Cb, and Cc are specifically disposed to
correspond to each of the plural cylinders 51a. Accordingly, the
cams Ca, Cb, and Cc are specifically used to drive the exhaust
valve 55 for each of the cylinders 51a. Specifically, the variable
valve mechanism 60 selects a use cam used to drive the exhaust
valve 55 out of the cams Ca, Cb, and Cc for each of the plural
cylinders 51a.
[0071] The variable valve mechanism 60 includes a cam contact
portion 61, a valve driving portion 62, a rocker arm portion 63,
and a rocker arm shaft 64. The cam contact portion 61, the valve
driving portion 62, and the rocker arm portion 63 are disposed for
each cylinder 51a and constitute a unit U.
[0072] The cam contact portions 61 are cam followers and the number
of cam contact portions disposed herein is two or more (three
herein) to correspond to the cams Ca, Cb, and Cc. The cam contact
portion 61a is a cam contact portion coming in contact with the cam
Ca out of the plural cam contact portions 61. The cam contact
portion 61b is a cam contact portion coming in contact with the cam
Cb and the cam contact portion 61c is a cam contact portion coming
in contact with the cam Cc. The plural cam contact portions 61 are
disposed in the rocker aim portion 63.
[0073] The valve driving portion 62 is disposed in the rocker aim
portion 63. The valve driving portions 62 are disposed to
correspond to the number (two herein) of exhaust valves 55 disposed
for each cylinder 51a, and transmit dynamic power to the exhaust
valves 55. The valve driving portion 62 may be a part of the rocker
arm portion 63.
[0074] The rocker arm portion 63 is a power relay portion and
relays dynamic power transmitted from the cam shaft 65 to the
exhaust valve 55 along with the cam contact portions 61 and the
valve driving portions 62. The rocker aim portion 63 has a shaft
hole Hs. The rocker arm shaft 64 is inserted (disposed) into the
shaft hole Hs. The rocker arm shaft 64 supports the rocker arm
portion 63 so as to fluctuate. The rocker arm shaft 64 is common to
the units U provided to the respective cylinders 51a. The rocker
arm shaft 64 is disposed in the extending direction of the cam
shaft 65.
[0075] FIG. 7 is a diagram schematically illustrating a
configuration of the unit U. FIG. 7 illustrates the unit U along
with the cam shaft 65. The rocker arm portion 63 specifically
includes fluctuation portions 63a, 63b, and 63c as plural
fluctuation portions. The fluctuation portions 63a, 63b, and 63c
individually fluctuate depending on the cam profiles of the cams
Ca, Cb, and Cc, and relay dynamic power to be transmitted from the
cam shaft 65 to the exhaust valve 55.
[0076] The fluctuation portion 63a as a first fluctuation portion
is provided with a cam contact portion 61a. Accordingly, the
fluctuation portion 63a fluctuates with the cam Ca. The fluctuation
portion 63b as a second fluctuation portion is provided with a cam
contact portion 61b, and the fluctuation portion 63c as a third
fluctuation portion is provided with a cam contact portion 61c.
Accordingly, the fluctuation portion 63b fluctuates with the cam Cb
and the fluctuation portion 63c fluctuates with the cam Cc.
[0077] The valve driving portions 62 are disposed in the
fluctuation portion 63b. Accordingly, the fluctuation portion 63b
out of the fluctuation portions 63a, 63b, and 63c in the rocker arm
portion 63 drives the exhaust valve 55. The fluctuation portions
63a, 63b, and 63c are supported by the rocker arm shaft 64 so as to
individually fluctuate. In this configuration, the shaft hole Hs is
specifically disposed to penetrate the fluctuation portions 63a,
63b, and 63c.
[0078] The rocker arm portion 63 includes coupling mechanisms 631,
632 as plural coupling mechanisms. The coupling mechanisms 631, 632
perform coupling and decoupling between two fluctuation portions
(specifically, two fluctuation portions adjacent to each other) out
of the fluctuation portions 63a, 63b, and 63c. Specifically, the
coupling mechanism 631 as a first coupling mechanism performs
coupling and decoupling between the fluctuation portion 63a and the
fluctuation portion 63b, and the coupling mechanism 632 as a second
coupling mechanism performs coupling and decoupling between the
fluctuation portion 63b and the fluctuation portion 63c.
[0079] The fluctuation portion 63a is provided with an impelling
member (for example, a return spring) that impels the cam contact
portion 61a to the cam Ca in a range in which the cam Ca can drive
the exhaust valve 55. Accordingly, the cam contact portion 61a
comes in contact with the cam Ca in a state where the coupling to
the fluctuation portion 63a is released. The same is true of the
fluctuation portion 63c. The impelling forces of the impelling
members are set to a range in which a predetermined cam out of the
cams Ca, Cb, and Cc can drive the exhaust valve 55 even when at
least one of the coupling between the fluctuation portions 63a, 63b
and the coupling between the fluctuation portions 63b, 63c is
performed.
[0080] FIG. 8 is a diagram illustrating the coupling mechanisms
631, 632. The coupling mechanism 631 is connected to an oil control
valve (OCV) 81 and the coupling mechanism 632 is connected to an
OCV 82. The OCV 81 transmits an oil pressure to the coupling
mechanism 631 when it is in an ON state, and opens the oil pressure
from the coupling mechanism 631 when it is in an OFF state. The OCV
82 transmits an oil pressure to the coupling mechanism 632 when it
is in an ON state, and opens the oil pressure from the coupling
mechanism 632 when it is in an OFF state.
[0081] A flow channel R1 connects the OCV 81 and the coupling
mechanism 631. A flow channel R2 connects the OCV 82 and the
coupling mechanism 632. The flow channels R1, R2 are independently
disposed. Each of the flow channels R1, R2 may be, for example, a
flow channel connected to the corresponding coupling mechanism out
of the coupling mechanisms 631, 632 via a member extending along
the cam shaft 65. At least one of the flow channels R1, R2 may be,
for example, a flow channel connected to the corresponding coupling
mechanism out of the coupling mechanisms 631, 632 via the rocker
aim shaft 64.
[0082] Specifically, the coupling mechanism 631 includes holding
portions H11, H12, pins Pn11, Pn12, and a spring Sp1. Specifically,
the coupling mechanism 632 includes holding portions H21, H22, pins
Pn21, Pn22, and a spring Sp2. The coupling mechanisms 631, 632 have
the same structure. Accordingly, the coupling mechanisms 631, 632
will be described below with the coupling mechanism 631 as an
example.
[0083] The holding portion H11 is disposed in the fluctuation
portion 63a and the holding portion H12 is disposed in the
fluctuation portion 63b. The holding portions H11, H12 are arranged
along the extending direction of the cam shaft 65 when the exhaust
valve 55 is not lifted. The holding portions H11, H12 have a
bottomed cylindrical shape and have the same inner diameter. Here,
the term "the same" includes a difference within a manufacturing
error. The same is true of the following description. The OCV 81 is
specifically connected to the inside of the holding portion H11
from the bottom of the holding portion H11 via the flow channel
R1.
[0084] The pin Pn11 is held by at least the holding portion H11 of
the holding portions H11, H12. The pin Pn12 is held by the holding
portion H12 of the holding portions H11, H12. The pins Pn11, Pn12
have a cylindrical shape and have the same outer diameter. The
outer diameter of the pins Pn11, Pn12 is set to be smaller by a
sliding clearance than the inner diameter of the holding portions
H11, H12. The spring Sp1 is disposed between the bottom of the
holding portion H12 and the pin Pn12. The spring Sp1 impels the pin
Pn12. The length of the spring Sp1 is set to a length with which
the pin Pn12 does not reach the holding portion H11.
[0085] The coupling mechanism 631 performs coupling between the
fluctuation portions 63a, 63b when the OCV 81 is in the ON state.
Specifically, in this case, in the state where the exhaust valve 55
is not lifted, the oil pressure transmitted via the OCV 81 causes
the pins Pn11, Pn12 to move together against the impelling force of
the spring Sp1. As a result, the pin Pn11 is held by the holding
portion H11 and the holding portion H12, whereby the fluctuation
portions 63a, 63b are coupled to each other.
[0086] The coupling mechanism 631 performs decoupling between the
fluctuation portions 63a, 63b when the OCV 81 is in the OFF state.
Specifically, in this case, in the state where the exhaust valve 55
is not lifted, the spring Sp1 causes the pins Pn11, Pn12 to move
together against the oil pressure opened via the OCV 81. As a
result, the pin Pn11 is held by the holding portion H11, whereby
the fluctuation portions 63a, 63b are decoupled from each
other.
[0087] In this way, in the coupling mechanism 631, specifically,
the pin Pn11 performs coupling and decoupling between the
fluctuation portions 63a, 63b. In the coupling mechanism 632, the
pin Pn21 performs coupling and decoupling between the fluctuation
portions 63b, 63c. The pin Pn11 is a first pin and is an example of
the first lock member. The pin Pn21 is a second pin and is an
example of the second lock member.
[0088] FIGS. 9A to 9C are diagrams illustrating use patterns of the
use cams. FIG. 9A illustrates a pattern Pt1 as a first pattern,
FIG. 9B illustrates a pattern Pt2 as a second pattern, and FIG. 9C
illustrates a pattern Pt3 as a third pattern. The fluctuation
portion 63a or the fluctuation portion 63c denoted by dotted lines
is in a decoupled state. The coupling mechanisms 631, 632 switch
the use pattern of the use cam to three or more patterns (three
patterns from the pattern Pt1 to the pattern Pt3).
[0089] The pattern Pt1 sets the use cam to the cam Ca. In this
case, the coupling mechanism 631 couples the fluctuation portions
63a, 63b and the second coupling mechanism 632 decouples the
fluctuation portions 63b, 63c. In this case, in terms of a coupling
mode, the exhaust valve 55 can be driven with the cams Ca, Cb. On
the other hand, the cam profiles of the cams Ca, Cb are set so that
the amount of lift of the exhaust valve 55 with the cam Ca is
greater than that with the cam Cb in each phase as described above.
Accordingly, in this case, the exhaust valve 55 is driven with the
cam Ca.
[0090] The pattern Pt2 sets the use cam to the cam Cb. In this
case, the coupling mechanism 631 decouples the fluctuation portions
63a, 63b from each other and the coupling mechanism 632 decouples
the fluctuation portions 63b, 63c from each other. In this case,
dynamic power is not transmitted from the first fluctuation portion
63a to the second fluctuation portion 63b. Similarly, dynamic power
is not transmitted from the third fluctuation portion 63c to the
second fluctuation portion 63b. Accordingly, in this case, the
exhaust valve 55 is driven with the cam Cb.
[0091] The pattern Pt3 sets the use cam to the cams Cb, Cc. In this
case, the coupling mechanism 631 decouples the fluctuation portions
63a, 63b from each other and the coupling mechanism 632 couples the
fluctuation portions 63b, 63c to each other. As a result, the
exhaust valve 55 is driven with the cams Cb, Cc. The unit U may
employ a use pattern in which the use cam is set to cams Ca, Cc. In
this case, the entire unit U is involved in the driving of the
exhaust valve 55 and thus the weight acting on the exhaust valve 55
increases. As a result, a valve bounce may occur in the exhaust
valve 55. Accordingly, the switching of the use cam to such a use
pattern is excluded herein.
[0092] The variable valve mechanism 60 is configured to switch the
cams such that a plurality of modes are performed. The cam
switching mode differs depending on the switching form of the use
cam. The switching form of the use cam is a form of switching from
one use pattern to the other use pattern between two use patterns
out of plural use patterns of the use cam.
[0093] The cam switching modes specifically include first to third
modes to be described below. In the first mode, the switching form
of the use cam is switching from a pattern Pt2 to a pattern Pt1
(that is, switching from the cam Cb to the cam Ca). In the second
mode, the switching form of the use cam is switching from the
pattern Pt2 to a pattern Pt3 (that is, switching from the cam Cb to
the cams Ca, Cc). In the third mode, the switching form of the use
cam is switching from the pattern Pt3 to the pattern Pt1 (that is,
switching from the cams Cb, Cc to the cam Ca). The plural modes as
the cam switching modes in the variable valve mechanism 60
specifically include total six modes of the first to third modes
and three modes in which the switching form of the use cam is
reverse in the first to third modes.
[0094] The ECU 70 illustrated in FIG. 1 or the like is an
electronic control unit, and the ECU 70 is electrically connected
to the EGR valve 43, the fuel injection valve 56, the OCVs 81, 82,
and the warning lamp 85 as control targets. The ECU is also
electrically connected to the air flowmeter 11, the in-cylinder
pressure sensor 91, a crank angle sensor 92 that detects a crank
angle .theta., an accelerator opening sensor 93 that gives an
acceleration request to the internal combustion engine 50, a
vehicle speed sensor 94 that detects a speed of a vehicle having
the internal combustion engine 50 mounted thereon, and oil pressure
sensors 95, 96 that detect oil pressures transmitted to the OCVs
81, 82 as sensor and switch types. The warning lamp 85 is a warning
unit and may be disposed, for example, in the interior of the
vehicle having the internal combustion engine 50 mounted
thereon.
[0095] In the ECU 70, the CPU performs processes using a temporary
memory area of a RAM on the basis of a program stored in a ROM if
necessary, whereby, for example, a determination unit and first to
fourth control units to be described below are embodied. This
configuration may be embodied, for example, by plural electronic
control units.
[0096] The determination unit determines whether switching
abnormality of a use cam in the variable valve mechanism 60 is
present on the basis of a locus M in a predetermined period K. The
predetermined period K is a period in which the exhaust valve 55 is
opened. The locus M is an in-cylinder pressure changing rate
dPc/d.theta. and is a locus indicating a variation of the
in-cylinder pressure changing rate dPc/d.theta. with respect to the
crank angle .theta.. The in-cylinder pressure changing rate
dPc/d.theta. is a pressure changing rate of the combustion chamber
E. In the internal combustion engine 50 having plural cylinders
51a, the in-cylinder pressure changing rate dPc/d.theta. of at
least one of the plural cylinders 51a is specifically employed as
the in-cylinder pressure changing rate dPc/d.theta..
[0097] FIG. 10 is a diagram illustrating the predetermined period
K. A lift curve La indicates a lift curve L of the exhaust valve 55
obtained when the exhaust valve 55 is driven in accordance with the
cam profile of the cam Ca. A lift curve Lb indicates a lift curve L
obtained when the exhaust valve 55 is driven in accordance with the
cam profile of the cam Cb. A lift curve Lc indicates a lift curve L
obtained when the exhaust valve 55 is driven in accordance with the
cam profile of the cam Cc.
[0098] The predetermined period K specifically includes valve
opening periods Ka, Kb, and Kc of the exhaust valve 55 when the
exhaust valve 55 is driven with the cams Ca, Cb, and Cc. In this
configuration, the determination unit determines whether the
switching abnormality is present on the basis of the cam switching
mode. In this case, when the switching of the use cam is normally
performed, the predetermined period K can be further specified as
at least one period (for example, the valve opening period Ka or
the valve opening periods Kb and Kc) of a period in which the
exhaust valve 55 is opened with the switching of the use cam and a
period in which the exhaust valve 55 is not opened with the
switching of the use cam.
[0099] The predetermined period K specified in this way on the
basis of the cam switching mode can be specified in advance
depending on the cam switching mode. The variable valve mechanism
60 can switch the use cam in a period other than the specified
predetermined period K. The predetermined period K can be further
specified as a period after the switching of the use cam has
started.
[0100] When determining whether the switching abnormality is
present on the basis of the locus M, the determination unit
determines whether the switching abnormality is present on the
basis of a predetermined item of the locus M. The predetermined
item includes at least one of presence, absence, value, and
generating timing of an inflection point obtained by the operation
of the exhaust valve 55. The inflection point will be described in
detail later.
[0101] When it is determined that switching abnormality is present
in at least one of the plural modes, the determination unit
determines that the variable valve mechanism 60 is abnormal. When
it is determined that the switching abnormality is not present in
all of the plural modes, the determination unit determines that the
variable valve mechanism 60 is normal. When determining whether the
switching abnormality is present, the determination unit
specifically determines whether abnormality is present in coupling
or decoupling that is performed by at least one of the pins Pn11,
Pn21.
[0102] The determination unit further determines the cam switching
state of the variable valve mechanism 60 on the basis of the cam
switching mode and the locus M in the predetermined period K. When
determining the cam switching state, the determination unit
specifically determines an abnormality form of the switching
abnormality of the use cam in the variable valve mechanism 60. The
abnormality form specifically includes mechanical failure and
responsiveness failure. The mechanical failure specifically
includes bounce, oblique insertion, fixation, and incomplete
separation of the pin Pn11 or the pin Pn21. The responsiveness
failure specifically includes a response delay of the switching
timing of the use cam caused between the coupling mechanisms 631,
632 in the unit U and a response delay of the switching timing of
the use cam caused between the cylinders 51a.
[0103] When determining presence or absence of the switching
abnormality and the abnormality form, the determination unit
specifically determines the abnormality form along with the
presence or absence of the switching abnormality. Specifically, the
determination unit simultaneously determines the presence or
absence of the switching abnormality and the abnormality form by
determining whether the switching abnormality is present on the
basis of plural determination methods different depending on the
abnormality forms.
[0104] When determining whether the switching abnormality is
present, the determination unit specifically repeatedly determines
whether the switching abnormality is present. When it is repeatedly
determined for a predetermined time that the switching abnormality
is present, the determination unit duly determines that the
switching abnormality is present. On the other hand, when it is
determined that the switching abnormality is not present before
repeatedly determining that the switching abnormality is present
for a predetermined time, the determination unit duly determines
that the switching abnormality is not present. When it is
determined that the switching abnormality is present before the
predetermined time elapses, the determination unit provisionally
determines that the switching abnormality is present.
[0105] The first control unit gives a warning when the
determination unit determines that the switching abnormality is
present. The first control unit specifically gives a warning by
turning on the warning lamp 85. The second control unit performs a
fail-safe control depending on the abnormality form determined by
the determination unit. The fail-safe control includes at least one
of limiting of a maximum vehicle speed in the vehicle having the
internal combustion engine 50 mounted thereon, limiting of a
maximum rotation speed of the internal combustion engine 50, and
limiting of an amount of fuel injected.
[0106] The third control unit limits an EGR ratio depending on the
abnormality form determined by the determination unit. The EGR
ratio is a ratio of the amount of exhaust air recirculated by
recirculation of exhaust air to the total amount of gas suctioned
into the cylinders. The fourth control unit performs re-switching
of the use cam when the determination unit provisionally determines
that the switching abnormality is present and determines that the
abnormality form of the switching abnormality is the bounce of the
pin Pn11 or the pin Pn21.
[0107] At the time of performing the fail-safe control, the second
control unit performs the fail-safe control when the determination
unit duly determines that the switching abnormality is present. The
fail-safe control performed by the second control unit may be the
same in some of the abnormality forms determined by the
determination unit. The second control unit can perform fail-safe
controls having different degrees such as a degree of limiting of
the maximum vehicle speed, a degree of limiting of the maximum
rotation speed, and a degree of limiting of the amount of fuel
injected in the abnormality forms on which the same type of
fail-safe control is performed out of the abnormality forms
determined by the determination unit. This is true of limiting of
the EGR ratio that is performed by the third control unit.
[0108] The ECU 70 by which the determination unit is embodied is an
example of an abnormality determining device. In addition, the ECU
70 by which the first control unit is embodied is an example of a
warning device, the ECU 70 by which the second control unit is
embodied is an example of a control device, the ECU 70 by which the
third control unit is embodied is an example of an EGR ratio
limiting device, and the ECU 70 by which the fourth control unit is
embodied is an example of a re-switching device. That is, the
internal combustion engine 50 is configured to include these
devices by including the ECU 70. These devices may be embodied by
the same electronic control unit or at least a part of the devices
may be embodied by different electronic control units. The warning
device may be understood to have a configuration including the
warning lamp 85 as a warning unit.
[0109] An example of an overall control of the abnormality
determination of determining whether the switching abnormality is
present will be described below with reference to the flowchart
illustrated in FIG. 11A and FIG. 11B. This flowchart can be
performed, for example, whenever the internal combustion engine 50
is started. The ECU 70 determines whether the abnormality
determination of determining whether the switching abnormality is
present is completed (step S1). In step S1, it is specifically
determined whether the presence or absence of the switching
abnormality is determined in all of the plural modes. When the
determination result of step S1 is positive, the flowchart
ends.
[0110] When the determination result of step S1 is negative, the
ECU 70 determines whether the switching of the use cam is performed
(step S2). Whether the switching of the use cam is performed can be
determined, for example, depending on whether a performance
condition of the switching of the use cam is established and
whether the switching of the use cam is completed. Whether the
switching of the use cam is completed can be determined, for
example, depending on whether a predetermined time elapses after
the performance condition of the switching of the use cam is
established. When the determination result of step S2 is negative,
the flowchart temporarily ends.
[0111] When the determination result of step S2 is positive, the
ECU 70 specifies the cam switching mode of the switching of the use
cam in performance (step S3). The cam switching mode can be
specified, for example, on the basis of the established performance
condition of the switching of the use cam. Subsequently, the ECU 70
determines whether the abnormality determination is uncompleted in
the specified mode (step S4). When the determination result is
negative, the flowchart temporarily ends. When the determination
result is positive, the ECU 70 determines whether it is in the
predetermined period K (step S5). When the determination result is
positive, the ECU 70 calculates the in-cylinder pressure changing
rate dPc/d.theta. (step S6).
[0112] Subsequently to step S6, the ECU 70 determines whether the
abnormality determination is present (whether it is determined that
the switching abnormality is present) (step S21). In step S21,
specifically, it is determined whether the switching abnormality is
present in any of the plural modes. When the determination result
of step S21 is negative, the ECU 70 determines whether the
abnormality determination is present in at least one of the plural
modes (step S23). When the determination result is positive, the
flowchart temporarily ends.
[0113] When the flowchart temporarily ends through the positive
determination of step S23 after the determination result of step S5
is positive, the in-cylinder pressure changing rate dPc/d.theta. is
calculated in step S6 whenever the determination result of step S5
in the subsequent routine is positive. As a result, the locus M in
the predetermined period K is obtained. On the other hand, when the
determination result of step S5 in the subsequent routine is
negative, the ECU 70 calculates an inflection point (step S11) and
determines whether the switching abnormality is present on the
basis of a predetermined item of the locus M (step S12). An example
of the specific determination that can be performed in step S12
will be described later.
[0114] When the determination result of step S12 is positive, the
ECU 70 determines that the switching abnormality is present in the
specified mode (step S13). In step S13, the ECU 70 can specifically
set a flag indicating that it is determined that the switching
abnormality is present to ON. In this case, through the positive
determination of step S21 subsequent thereto, the ECU 70 turns on
the warning lamp 85 (step S22).
[0115] When the determination result of step S12 is negative, the
ECU 70 determines that the switching abnormality is not present in
the specified mode (step S14). In step S14, the ECU 70 can
specifically set a flag indicating that it is determined that the
switching abnormality is not present in the specified mode to ON.
In this case, the determination result of step S21 subsequent
thereto is negative. When it is determined in step S14 that the
switching abnormality is not present in the plural modes, the
determination result of step S23 is negative.
[0116] Subsequently to step S22 or the negative determination of
step S23, the ECU 70 completes the abnormality determination (step
S24). In step S24, the ECU 70 can specifically set a flag
indicating that it is completely determined whether the switching
abnormality is present to ON. After step S24, the flowchart ends.
When the flowchart ends through the negative determination of step
S23 and step S24, for example, the abnormality determination in the
respective modes is reset to an incomplete state and then the
flowchart may be restarted.
[0117] The mechanical failure in the first mode, the mechanical
failure in the second mode, the mechanical failure in the third
mode, the first responsiveness failure, and the second
responsiveness failure will be sequentially described below
individually and specifically.
[0118] FIGS. 12A to 12F are diagrams illustrating the first
mechanical failure in the first mode. FIGS. 12A to 12F illustrate
an example where the mechanical failure is the bounce of the pin
Pn11. FIG. 12A is a diagram illustrating the state of the unit U
based on the mechanical failure. FIG. 12B is a diagram illustrating
an amount of lift of the exhaust valve 55 with respect to the crank
angle .theta.. FIG. 12C is a diagram illustrating a variation of
the in-cylinder pressure changing rate dPc/d.theta. with respect to
the crank angle .theta.. FIG. 12D is a diagram illustrating a
variation of the in-cylinder pressure Pc with respect to the crank
angle .theta.. FIG. 12E is an enlarged view of a part of FIG. 12D
in the scale of the vertical axis. FIG. 12F is a diagram
illustrating a variation of the in-cylinder pressure changing rate
dPc/d.theta. corresponding to FIGS. 12D and 12E. The scale of the
horizontal axis in FIGS. 12D, 12E, and 12F is the same, but the
scale of the horizontal axis in FIGS. 12B and 12C is not the
same.
[0119] As illustrated in FIG. 12A, when the bounce of the pin Pn11
occurs in the first mode in which the fluctuation portions 63a, 63b
are coupled, the exhaust valve 55 to be driven with the cam Ca is
driven with the cam Cb on the way. As a result, as illustrated in
FIG. 12B, the lift curve L of the exhaust valve 55 describes a
curve transitioning from the lift curve La to the lift curve Lb. As
illustrated in FIG. 12B, in other words, the cam profiles of the
cams Ca, Cb are set so that the lift curve Lb is included in the
lift curve La.
[0120] As illustrated in FIG. 12C, in this case, the locus M
describes the following locus. That is, the locus describes a locus
transitioning from a locus Ma, which is the locus M obtained when
the exhaust valve 55 is driven in accordance with the cam profile
of the cam Ca, to a locus Mb, which is the locus M obtained when
the exhaust valve 55 is driven in accordance with the cam profile
of the cam Cb. As a result, two inflection points MP1 as the first
inflection point appear in the locus M.
[0121] The inflection points MP1 are inflection points obtained
with the operation of the exhaust valve 55 based on at least one of
the cams Ca, Cb in the locus M. Specifically, the inflection point
MP1 is an inflection point appearing due to a variation of the
in-cylinder pressure Pc with the operation of the exhaust valve 55
based on at least one of the cams Ca, Cb in the locus M.
[0122] Specifically, the two inflection points MP1 appear due to
the variation of the in-cylinder pressure Pc to be described later.
That is, in this case, the in-cylinder pressure Pc varies with the
opening of the exhaust valve 55 and also varies with the transition
of the lift curve L from the lift curve La to the lift curve Lb
(the variation of the opening operation of the exhaust valve 55).
As a result, as illustrated in FIGS. 12D and 12E, a step based on
the opening of the exhaust valve 55 and a step based on the
transition of the lift curve L appear in the curve of the
in-cylinder pressure Pc. Accordingly, in this case, the inflection
points MP1 appear due to the steps as illustrated in FIG. 12F.
[0123] Therefore, the determination unit determines that the
switching abnormality is present when the cam switching mode is the
first mode and plural inflection points MP1 appear in the locus M.
The determination unit also determines that the abnormality form is
the bounce of the pin Pn11. When it is duly determined that the
abnormality form is the bounce of the pin Pn11, the second control
unit can perform, for example, the limiting of the maximum rotation
speed of the internal combustion engine 50 and the limiting of the
amount of fuel injected. The second control unit may perform the
limiting of the maximum vehicle speed instead of the limiting of
the maximum rotation speed or in addition to the limiting of the
maximum rotation speed.
[0124] FIGS. 13A to 13F are diagrams illustrating the second
mechanical failure in the first mode. FIGS. 13A to 13F illustrate
an example where the mechanical failure is the oblique insertion of
the pin Pn11. FIGS. 13A to 13F are the same diagrams as FIGS. 12A
to 12F.
[0125] As illustrated in FIG. 13A, when the oblique insertion of
the pin Pn11 occurs in the first mode, the exhaust valve 55 is
driven with the cam Ca while generating lift loss. As a result, as
illustrated in FIG. 13B, the lift curve L of the exhaust valve 55
describes a curve located between the lift curves La, Lb.
Accordingly, the locus M describes a locus other than the loci Ma,
Mb as illustrated in FIG. 13C. As a result, the inflection point
MP1 appears in a phase different from that of the inflection point
MPa. The inflection point MPa is a first predetermined inflection
point and is an inflection point obtained with the operation of the
exhaust valve 55 based on the cam Ca when the exhaust valve 55 is
driven in accordance with the camp profile of the cam Ca in the
locus M. Accordingly, the inflection point MPa is present on the
locus Ma.
[0126] Specifically, the inflection point MP1 appears as described
above with the variation of the in-cylinder pressure Pc to be
described below. That is, as illustrated in FIGS. 13D and 13E, in
this case, the delay of the opening timing of the exhaust valve 55
due to the lift loss delays the variation of the in-cylinder
pressure Pc generated with the opening of the exhaust valve 55.
Accordingly, in this case, the inflection point MP1 appears in a
phase different by a deviation T.sub.11 from that of the inflection
point MPa as illustrated in FIG. 13F. The deviation T.sub.11 is a
deviation (a first deviation herein) with respect to the inflection
point MP1 and represents the magnitude of a phase difference
between the inflection points MP1, MPa. An inflection point set in
advance can be used as the inflection point MPa. The inflection
point MPa may be set depending on a parameter affecting the
inflection point MPa. This is true of inflection points MPb, MPc to
be described later.
[0127] Therefore, when the cam switching mode is the first mode,
one inflection point MP1 appears in the locus M, and the inflection
point MP1 is an inflection point of which the deviation T.sub.11 is
greater than a predetermined value .alpha. (greater than or equal
to the predetermined value .alpha. herein), the determination unit
determines that the switching abnormality is present. The
determination unit also determines that the abnormality form is the
oblique insertion of the pin Pn11. When it is duly determined that
the abnormality form is the oblique insertion of the pin Pn11, the
second control unit can perform, for example, at least the limiting
of the maximum rotation speed of the limiting of the maximum
rotation speed of the internal combustion engine 50 and the
limiting of the amount of fuel injected.
[0128] FIGS. 14A to 14F are diagrams illustrating the third
mechanical failure in the first mode. FIGS. 14A to 14F illustrate
an example where the mechanical failure is the fixation of the pin
Pn11. FIGS. 14A to 14F are the same diagrams as FIGS. 12A to
12F.
[0129] As illustrated in FIG. 14A, when the fixation of the pin
Pn11 occurs in the first mode, the exhaust valve 55 is driven with
the cam Cb. Accordingly, as illustrated in FIG. 14B, the lift curve
L of the exhaust valve 55 is the same as the lift curve Lb. In this
case, the locus M is the same as the locus Mb as illustrated in
FIG. 14C. As a result, the inflection point MP1 is the same as the
inflection point MPb. That is, the inflection point MP1 is
immovable. The inflection point MPb is an inflection point of the
locus Mb. In this case, as illustrated in FIGS. 14D and 14E, the
variation of the in-cylinder pressure Pc is maintained in the
variation based on the cam Cb. Accordingly, as illustrated in FIG.
14F, the inflection point MP1 is immovable.
[0130] Therefore, when the cam switching mode is the first mode,
one inflection point MP1 appears in the locus M, and the inflection
point MP1 is immovable before and after the switching of the use
cam based on the first mode, the determination unit determines that
the switching abnormality is present. The determination unit
determines that the abnormality form is the fixation of the pin
Pn11. When it is duly determined that the abnormality form is the
fixation of the pin Pn11, the second control unit can perform, for
example, the limiting of the maximum rotation speed of the internal
combustion engine 50 and the limiting of the amount of fuel
injected. Specifically, whether the inflection point MP1 is
immovable can be determined on the basis of a deviation T.sub.12 to
be described later.
[0131] The determination unit, which determines the abnormality
form as described above when the cam switching mode is the first
mode, determines the abnormality form on the basis of the cam
switching mode and the inflection point MP1 when the cam switching
mode is the first mode.
[0132] A first control example will be described below with
reference to the flowcharts illustrated in FIGS. 15 to 18. The
first control example is an example of an individual control
operation of causing the ECU 70 to perform an operation of
switching the use cam based on the first mode and to determine
whether the switching abnormality due to the mechanical failure is
present in the switching operation. In the first control example,
it is determined whether the switching abnormality is present in
any of the plural cylinders 51a. Whether the switching abnormality
is present may be determined in each of the plural cylinders
51a.
[0133] The ECU 70 determines whether a switching request for
switching the use cam from the cam Cb to the cam Ca is given (step
S101). When it is duly determined that the switching request for
the use cam is given, or when it is duly determined that the
switching abnormality due to the mechanical failure is not present,
the switching request for the use cam can be stopped. When the
determination result is positive, the ECU 70 determines whether an
oil pressure and the in-cylinder pressure Pc can be detected (step
S102). In step S102, it is specifically determined whether the
variable valve mechanism 60 can be operated and whether presence or
absence of the switching abnormality can be determined.
[0134] When the determination results of steps S101, S102 are
negative, the control process flow returns to step S101. When the
determination result of step S102 is positive, the ECU 70 starts
detection of the in-cylinder pressure Pc with respect to the crank
angle .theta. and starts calculation of the in-cylinder pressure
changing rate dPc/d.theta. (step S103). The detection of the
in-cylinder pressure Pc and the calculation of the in-cylinder
pressure changing rate dPc/d.theta. can be stopped when the
sub-routine of mechanical failure determination A described in step
S105 ends.
[0135] The detection of the in-cylinder pressure Pc and the
calculation of the in-cylinder pressure changing rate dPc/d.theta.
may be performed, for example, independently. The calculated
in-cylinder pressure changing rate dPc/d.theta. may be subjected to
a noise removing process necessary for calculating an appropriate
inflection point from the locus M, or the like. Subsequently to
step S103, the ECU 70 turns on the OCV 81 (step S104). Accordingly,
the operation of switching the use cam based on the first mode is
performed. Subsequently, the ECU 70 performs mechanical failure
determination A (step S105).
[0136] Mechanical failure determination A is illustrated as a
sub-routine in the flowchart illustrated in FIGS. 16 to 18. In
FIGS. 16 to 18, it is determined whether the switching abnormality
is present using plural (three herein) determination methods
different depending on the abnormality forms (the bounce, the
oblique insertion, and the fixation of the pin Pn11 herein) of the
switching abnormality.
[0137] In the sub-routine of mechanical failure determination A,
the ECU 70 calculates the number of inflection points N (step
S111). The number of inflection points N can be calculated by
calculating the inflection point MP1. Subsequently, the ECU 70
determines whether the calculated number of inflection points N is
greater than or equal to two (step S112). In step S112, it is
determined whether the switching abnormality is present and whether
the abnormality form is the bounce of the pin Pn11. Accordingly,
when the determination result of step S112 is positive, the ECU 70
sets a flag A1' to ON (step S113). The flag A1' is a temporary
abnormality flag indicating that it is provisionally determined
that the switching abnormality is present and it is determined that
the abnormality form is the bounce of the pin Pn11.
[0138] Subsequently to step S113, the ECU 70 turns off the OCV 81
(step S114) and determines whether the state where the flag A1' is
in the ON state is maintained for a predetermined time (step S115).
At the time of the determination, the time in which the state where
the predetermined flag (flag A1' herein) is in the ON state is
maintained can be set to, for example, the time corresponding to
the number of combustion cycles from the combustion cycle in which
the predetermined flag is first set to the ON state. The
predetermined time may not be constant in the abnormal forms. When
the determination result of step S115 is negative, the sub-routine
of mechanical failure determination A ends. In this case, the
control process flow returns to the flowchart illustrated in FIG.
15. Thereafter, when the determination result of step S112 is
positive and the determination result of step S115 is negative, the
flag A1' is maintained in the ON state and it is provisionally
determined that the switching abnormality is present. In the
meantime, the re-switching of the use cam is performed.
[0139] When the determination result of step S115 is positive, the
ECU 70 sets the flag A1' to OFF and sets a flag A1 to ON (step
S116). The flag A1 is a due abnormality flag indicating that it is
duly determined that the switching abnormality is present and it is
determined that the abnormality form is the bounce of the pin
Pn11.
[0140] In this case, the ECU 70 limits the maximum rotation speed
of the internal combustion engine 50 and limits the amount of fuel
injected (step S117). The limiting of the amount of fuel injected
can be performed for each of the plural cylinders 51a. The limiting
of the amount of fuel injected may be performed, for example, on a
cylinder in which it is duly determined that the switching
abnormality is present out of the plural cylinders 51a. After step
S117, the sub-routine of mechanical failure determination A
ends.
[0141] When the determination result of step S112 is negative, the
ECU 70 sets the flag A1' to OFF (step S118). Accordingly, it is
duly determined that the switching abnormality of which the
abnormality form is the bounce of the pin Pn11 is not present.
Here, the determination of the ECU 70 for the switching abnormality
is expressed by ON and OFF of the flag, but this determination may
not be necessarily expressed by a flag.
[0142] Subsequently to step S118, the ECU 70 calculates the
deviation T.sub.11 (step S121) and determines whether the
calculated deviation T.sub.11 is greater than or equal to a
predetermined value .alpha. (step S122). In step S122, it is
determined whether the switching abnormality is present and whether
the abnormality form is the oblique insertion of the pin Pn11.
Accordingly, when the determination result of step S122 is
positive, the ECU 70 sets a flag A2' to ON (step S123). The flag
A2' is a flag indicating that it is provisionally determined that
the switching abnormality is present and it is determined that the
abnormality form is the oblique insertion of the pin Pn11.
[0143] Subsequently to step S123, the ECU 70 determines whether the
state where the flag A2' is in the ON state is maintained for a
predetermined time (step S124). When the determination result is
negative, the control process flow returns to step S121. In this
case, the deviation T.sub.11 in a combustion cycle next to the
combustion cycle in which the deviation T.sub.11 is previously
calculated is calculated in step S121. When the determination
result of step S124 is positive, the ECU 70 sets the flag A2' to
OFF and sets a flag A2 to ON (step S125).
[0144] The flag A2 is a due abnormality flag indicating that it is
duly determined that the switching abnormality is present and it is
determined that the abnormality form is the oblique insertion of
the pin Pn11. In this case, the ECU 70 limits the maximum rotation
speed of the internal combustion engine 50 and limits the amount of
fuel injected (step S126). In step S126, the ECU 70 can perform,
for example, the limiting of the maximum rotation speed or the
limiting of the amount of fuel injected having a degree different
from that in step S117. After step S126, the sub-routine of
mechanical failure determination A ends.
[0145] When the determination result of step S122 is negative, the
ECU 70 sets the flag A2' to OFF (step S127). Accordingly, it is
duly determined that the switching abnormality of which the
abnormality form is the oblique insertion of the pin Pn11 is not
present.
[0146] Subsequently to step S127, the ECU 70 calculates the
deviation T.sub.12 (step S131) and determines whether the
calculated deviation T.sub.12 is zero (step S132). The deviation
T.sub.12 is a second deviation with respect to the inflection point
MP1 and represents the magnitude of a phase difference between the
inflection points MP1 in the loci M obtained before and after the
use cam is switched in the first mode. Accordingly, it is
determined in step S132 whether the inflection points MP1 are
immovable and it is thus determined whether the switching
abnormality is present and whether the abnormality form is the
fixation of the pin Pn11. Whether the inflection points MP1 are
immovable may be determined, for example, depending on whether the
deviation T.sub.12 is smaller than a predetermined value.
[0147] When the determination result of step S132 is positive, the
ECU 70 sets a flag A3' to ON (step S133). The flag A3' is a
temporary abnormality flag indicating that it is provisionally
determined that the switching abnormality is present and it is
determined that the abnormality form is the fixation of the pin
Pn11. Subsequently to step S133, the ECU 70 determines whether the
state where the flag A3' is in the ON state is maintained for a
predetermined time (step S134). When the determination result is
negative, the control process flow returns to step S131. In this
case, in step S131, the deviation T.sub.12 is calculated on the
basis of the inflection point MP1 in a combustion cycle next to the
combustion cycle in which the deviation T.sub.12 is previously
calculated as the inflection point MP1 obtained after the switching
of the use cam is performed.
[0148] When the determination result of step S134 is positive, the
ECU 70 sets the flag A3' to OFF and sets a flag A3 to ON (step
S135). The flag A3 is a due abnormality flag indicating that it is
duly determined that the switching abnormality is present and it is
determined that the abnormality form is the fixation of the pin
Pn11. In this case, the ECU 70 limits the maximum rotation speed of
the internal combustion engine 50 and limits the amount of fuel
injected (step S136). After step S136, the sub-routine of
mechanical failure determination A ends.
[0149] When the determination result of step S132 is negative, the
ECU 70 sets the flag A3' to OFF (step S137). Accordingly, it is
duly determined that the switching abnormality of which the
abnormality form is the fixation of the pin Pn11 is not present. In
this case, since the determination results of steps S112, S122, and
S132 are negative, it is duly determined that the switching
abnormality based on the mechanical failure is not present. After
step S137, the sub-routine of mechanical failure determination A
ends.
[0150] FIGS. 19A to 19F are diagrams illustrating the first
mechanical failure in the second mode. FIGS. 19A to 19F illustrate
an example where the mechanical failure is the bounce of the pint
Pn21. FIGS. 19A to 19F are the same diagrams as FIGS. 12A to
12F.
[0151] As illustrated in FIG. 19A, when the bounce of the pin Pn21
occurs in the second mode in which the fluctuation portions 63b,
63c are coupled, the opening operation of the exhaust valve 55 to
be driven with the cam Ca is stopped. As a result, as illustrated
in FIG. 19B, the lift curve L of the exhaust valve 55 describes a
curve departing and falling from the lift curve Lc in the way. As
illustrated in FIG. 19C, in this case, the locus M describes the
following locus. That is, the locus describes a locus departing and
falling from the locus Mc, which is the locus M obtained when the
exhaust valve 55 is driven in accordance with the cam profile of
the cam Cc, in the middle way. As a result, an inflection points
MP2 as the second inflection point appears in a phase different
from that of the inflection point MPc.
[0152] The inflection point MP2 is an inflection point obtained
with the operation of the exhaust valve 55 based on the cam Cc in
the locus M. Specifically, the inflection point MP2 is an
inflection point appearing due to the variation of the in-cylinder
pressure Pc with the operation of the exhaust valve 55 based on the
cam Cc in the locus M. The inflection point MPc is a second
predetermined inflection point and is an inflection point obtained
with the operation of the exhaust valve 55 based on the cam Cc when
the exhaust valve 55 is driven in accordance with the profile of
the cam Cc in the locus M. Accordingly, the inflection point MPc is
present on the locus Mc.
[0153] Specifically, the inflection point MP2 appears as described
above due to the variation in the in-cylinder pressure Pc to be
described below. That is, as illustrated in FIGS. 19D and 19E, in
this case, the in-cylinder pressure Pc varies with the stopping of
the opening operation of the exhaust valve 55. Accordingly, in this
case, the inflection point MP2 appears in a phase different by a
deviation T.sub.21 from that of the inflection point MPc as
illustrated in FIG. 19F. The deviation T.sub.21 is a first
deviation with respect to the inflection point MP2 and represents
the magnitude of a phase difference between the inflection points
MP2, MPc.
[0154] Therefore, when the cam switching mode is the second mode
the inflection point MP2 appears in the locus M, and the inflection
point MP2 is an inflection point at which the deviation T.sub.21 is
greater than a predetermined value .beta..sub.T (greater than or
equal to the predetermined value .beta..sub.T herein), the
determination unit determines that the switching abnormality is
present. The determination unit determines that the abnormality
form is the bounce of the pin Pn21. When it is duly determined that
the abnormality form is the bounce of the pin Pn21, the second
control unit can perform, for example, the limiting of the maximum
rotation speed of the internal combustion engine 50 and the
limiting of the amount of fuel injected.
[0155] FIGS. 20A to 20F are diagrams illustrating the second
mechanical failure in the second mode. FIGS. 20A to 20F illustrate
an example where the mechanical failure is the oblique insertion of
the pint Pn21. FIGS. 20A to 20F are the same diagrams as FIGS. 12A
to 12F.
[0156] As illustrated in FIG. 20A, when the oblique insertion of
the pin Pn21 occurs in the second mode, the exhaust valve 55 is
driven with the cam Cc while generating lift loss. As a result, as
illustrated in FIG. 20B, the lift curve L of the exhaust valve 55
describes a curve of which the amount of lift is smaller than that
of the lift curve Lc as a whole. As illustrated in FIG. 20C, in
this case, the phase is equivalent between the inflection points
MP2, MPc, but the value (the in-cylinder pressure changing rate
dPc/d.theta.) thereof differs between the inflection points MP2,
MPc. Specifically, the inflection point MP2 appears with the
variation of the in-cylinder pressure Pc to be described below.
[0157] That is, as illustrated in FIGS. 20D and 20E, in this case,
the in-cylinder pressure Pc falls due to the lift loss.
Accordingly, in this case, the value differs by a deviation
P.sub.21 between the inflection points MP2, MPc as illustrated in
FIG. 20F. The deviation P.sub.21 is a second deviation with respect
to the inflection point MP2 and represents the magnitude of a
difference between the value of the inflection point MP2 and the
value of the inflection point MPc.
[0158] Therefore, when the cam switching mode is the second mode,
the inflection point MP2 appears in the locus M, and the inflection
point MP2 is an inflection point at which the deviation T.sub.21 is
smaller than a predetermined value .beta..sub.T and the deviation
P.sub.21 is greater than a predetermined value .beta..sub.P
(greater than or equal to the predetermined value .beta..sub.P
herein), the determination unit determines that the switching
abnormality is present. The determination unit also determines that
the abnormality form is the oblique insertion of the pin Pn21. When
it is duly determined that the abnormality form is the oblique
insertion of the pin Pn21, the second control unit can perform, for
example, the limiting of the maximum rotation speed of the internal
combustion engine 50 and the limiting of the amount of fuel
injected. The third control unit can perform the decreasing of the
EGR ratio.
[0159] FIGS. 21A to 21F are diagrams illustrating the third
mechanical failure in the second mode. FIGS. 21A to 21F illustrate
an example where the mechanical failure is the fixation of the pint
Pn21. FIGS. 21A to 21F are the same diagrams as FIGS. 12A to
12F.
[0160] As illustrated in FIG. 21A, when the fixation of the pin
Pn21 occurs in the second mode, the exhaust valve 55 is not driven
with the cam Cc. Accordingly, as illustrated in FIG. 21B, the lift
curve L of the exhaust valve 55 does not vary with the cam Cc. In
this case, the locus M does not vary with the cam Cc as illustrated
in FIG. 21C. As a result, the inflection point MP2 does not appear.
In this case, the in-cylinder pressure Pc does not vary with the
cam Cc as illustrated in FIGS. 21D and 21F. As a result, the
inflection point MP2 does not appear as illustrated in FIG.
21F.
[0161] Therefore, when the cam switching mode is the second mode
and the inflection point MP2 does not appear in the locus M, the
determination unit determines that the switching abnormality is
present. The determination unit determines that the abnormality
form is the fixation of the pin Pn21. When it is duly determined
that the abnormality form is the fixation of the pin Pn21, the
second control unit can perform, for example, the limiting of the
maximum rotation speed of the internal combustion engine 50 and the
limiting of the amount of fuel injected. The third control unit can
perform the decreasing of the EGR ratio.
[0162] The determination unit, which determines the abnormality
form as described above when the cam switching mode is the second
mode, determines the abnormality form on the basis of the cam
switching mode and the inflection point MP2 when the cam switching
mode is the second mode. The determination of the determination
unit of the abnormality form on the basis of the inflection point
MP2 includes the determination of the determination unit of the
abnormality form on the basis of the presence or absence of the
inflection point MP2.
[0163] A second control example will be described below with
reference to the flowcharts illustrated in FIGS. 22 to 25. The
second control example is an example of an individual control
operation of causing the ECU 70 to perform an operation of
switching the use cam based on the second mode and to determine
whether the switching abnormality due to the mechanical failure is
present in the switching operation. Whether the switching
abnormality is present may be determined in each of the plural
cylinders 51a as in the first control example. In the following
description, description of the same control operations as the
above-mentioned control operations will not be appropriately
repeated.
[0164] The ECU 70 determines whether a switching request for
switching the use cam from the cam Cb to the cams Ca, Cc is given
(step S201). When the determination result is positive, the ECU 70
turns on the OCV 82 through the determination result of step S202
and step S203 (step S204). Accordingly, the operation of switching
the use cam in the second mode is performed. Subsequently, the ECU
70 performs mechanical failure determination B (step S205).
Mechanical failure determination B is illustrated as a sub-routine
in the flowcharts illustrated in FIGS. 23 to 25.
[0165] In the sub-routine of mechanical failure determination B,
the ECU 70 calculates a deviation T.sub.21 (step S211) and
determines whether the calculated deviation T.sub.21 is greater
than or equal to a predetermined value .beta..sub.T (step S212). In
step S212, it is determined whether the switching abnormality is
present and whether the abnormality form thereof is the bounce of
the pin Pn21. The determination result of step S212 is negative
when the inflection point MP2 does not appear and the deviation
T.sub.21 cannot be calculated.
[0166] When the determination result of step S212 is positive, the
ECU 70 sets a flag B1' to ON (step S213). The flag B1' is a
temporary abnormality flag indicating that it is provisionally
determined that the switching abnormality is present and it is
determined that the abnormality form is the bounce of the pin
Pn21.
[0167] Subsequently to step S213, the ECU 70 turns off the OCV 82
(step S214) and determines whether the state where the flag B1' is
in the ON state is maintained for a predetermined time (step S215).
When the determination result is negative, the sub-routine of
mechanical failure determination B ends. In this case, the
re-switching of the use cam is performed. When the determination
result of step S215 is positive, the ECU 70 sets the flag B1' to
OFF and sets a flag B1 to ON (step S216).
[0168] The flag B1 is a due abnormality flag indicating that it is
duly determined that the switching abnormality is present and it is
determined that the abnormality form is the bounce of the pin Pn21.
In this case, the ECU 70 limits the maximum rotation speed of the
internal combustion engine 50 and limits the amount of fuel
injected (step S217). After step S217, the sub-routine of
mechanical failure determination B ends.
[0169] When the determination result of step S212 is negative, the
ECU 70 sets the flag B1' to OFF (step S218). Accordingly, it is
duly determined that the switching abnormality of which the
abnormality form is the bounce of the pin Pn21 is not present.
[0170] Subsequently to step S218, the ECU 70 calculates the
deviation P.sub.21 (step S221) and determines whether the
calculated deviation P.sub.21 is greater than or equal to a
predetermined value .beta..sub.P (step S222). In step S222, it is
determined whether the switching abnormality is present and whether
the abnormality form is the oblique insertion of the pin Pn21.
Accordingly, when the determination result of step S222 is
positive, the ECU 70 sets a flag B2' to ON (step S223). The flag
B2' is a flag indicating that it is provisionally determined that
the switching abnormality is present and it is determined that the
abnormality form is the oblique insertion of the pin Pn21.
[0171] Subsequently to step S223, the ECU 70 determines whether the
state where the flag B2' is in the ON state is maintained for a
predetermined time (step S224). When the determination result is
negative, the control process flow returns to step S221. In step
S221, as the value of the inflection point MP2 obtained after the
switching operation of the use cam, the deviation P.sub.21 is
calculated on the basis of the inflection point MP2 in a combustion
cycle next to the combustion cycle in which the deviation P.sub.21
is previously calculated.
[0172] When the determination result of step S224 is positive, the
ECU 70 sets the flag B2' to OFF and sets a flag B2 to ON (step
S225). The flag B2 is a due abnormality flag indicating that it is
duly determined that the switching abnormality is present and it is
determined that the abnormality form is the oblique insertion of
the pin Pn21. In this case, the ECU 70 limits the maximum rotation
speed and the amount of fuel injected of the internal combustion
engine 50 and decreases the EGR ratio (step S226). After step S226,
the sub-routine of mechanical failure determination B ends.
[0173] When the determination result of step S222 is negative, the
ECU 70 sets the flag B2' to OFF (step S227). Accordingly, it is
duly determined that the switching abnormality of which the
abnormality form is the oblique insertion of the pin Pn21 is not
present. In step S222, the determination result is negative even
when the inflection point MP2 does not appear and the deviation
P.sub.21 cannot be calculated.
[0174] Subsequently to step S227, the ECU 70 calculates the
deviation P.sub.22 (step S231) and determines whether the
calculated deviation P.sub.22 is zero (step S232). The deviation
P.sub.22 is a third deviation with respect to the inflection point
MP2 and represents the magnitude of a difference between the
in-cylinder pressure changing rates dPc/d.theta. obtained from the
phase of the inflection point MPc in the loci M obtained before and
after the use cam is switched in the third mode. In step S232, it
is determined whether the inflection point MP2 appears, and it is
determined that the inflection point MP2 does not appear when the
deviation P.sub.22 is zero. Whether the inflection point MP2
appears may be determined, for example, depending on whether the
deviation P.sub.22 is smaller than a predetermined value.
[0175] Specifically, it is determined in step S232 whether the
switching abnormality is present and whether the abnormality form
is the fixation of the pin Pn21. Accordingly, when the
determination result of step S232 is positive, the ECU 70 sets a
flag B3' to ON (step S233). The flag B3' is a temporary abnormality
flag indicating that it is provisionally determined that the
switching abnormality is present and it is determined that the
abnormality form is the fixation of the pin Pn21. Subsequently to
step S233, the ECU 70 determines whether the state where the flag
B3' is in the ON state is maintained for a predetermined time (step
S234). When the determination result is negative, the sub-routine
of mechanical failure determination B ends.
[0176] When the determination result of step S234 is positive, the
ECU 70 sets the flag B3' to OFF and sets a flag B3 to ON (step
S235). The flag B3 is a due abnormality flag indicating that it is
duly determined that the switching abnormality is present and it is
determined that the abnormality form is the fixation of the pin
Pn21. In this case, the ECU 70 limits the maximum rotation speed
and the amount of fuel injected of the internal combustion engine
50 and decreases the EGR ratio (step S236). After step S236, the
sub-routine of mechanical failure determination B ends.
[0177] When the determination result of step S232 is negative, the
ECU 70 sets the flag B3' to OFF (step S237). Accordingly, it is
duly determined that the switching abnormality of which the
abnormality form is the fixation of the pin Pn21 is not present. In
this case, since the determination results of steps S212, S222, and
S232 are negative, it is duly determined that the switching
abnormality based on the mechanical failure is not present. After
step S237, the sub-routine of mechanical failure determination B
ends.
[0178] FIGS. 26A to 26I are diagrams illustrating the mechanical
failure in the third mode. In the third mode, the mechanical
failure may occur in the respective coupling mechanisms 631, 632.
The mechanical failure occurring in the coupling mechanism 631 is
the same as the mechanical failure in the first mode. Accordingly,
the description of the mechanical failure occurring in the coupling
mechanism 631 will not be repeated.
[0179] FIGS. 26A to 26C illustrate a case where the mechanical
failure is the bounce of the pin Pn21. FIGS. 26D to 26F illustrate
a case where the mechanical failure is the incomplete detachment of
the pin Pn21 and FIGS. 26G to 26I illustrate a case where the
mechanical failure is the fixation of the pin Pn21. FIGS. 26A, 26D,
and 26G are the same diagrams as FIG. 12A. FIGS. 26B, 26E, and 26H
are the same diagrams as FIG. 12B. FIGS. 26C, 26F, and 26I are the
same diagrams as FIG. 12C.
[0180] As illustrated in FIGS. 26A and 26B, when the bounce of the
pin Pn21 occurs in the third mode in which the fluctuation portions
63b, 63c are decoupled, the exhaust valve 55 is temporarily driven
with the cam Cc. in this case, the inflection point MP2 that does
not appear at the time of normality appears as illustrated in FIG.
26C. In this case, the inflection point MP2 appears in a phase
different from that of the inflection point MPc.
[0181] Therefore, when the cam switching mode is the third mode,
the inflection point MP2 appears in the locus M, and the inflection
point MP2 is an inflection point at which the deviation T.sub.21 is
greater than a predetermined value .beta..sub.T, the determination
unit determines that the switching abnormality of the variable
valve mechanism 60 is present. The determination unit determines
that the abnormality form is the bounce of the pin Pn21. When it is
duly determined that the abnormality form is the bounce of the pin
Pn21, the second control unit can perform, for example, the
limiting of the maximum rotation speed of the internal combustion
engine 50 and the limiting of the amount of fuel injected.
[0182] As illustrated in FIGS. 26D and 26E, when the incomplete
detachment of the pin Pn21 occurs in the third mode, the exhaust
valve 55 is driven with the cam Cc while generating lift loss. In
this case, the inflection point MP2 that does not appear at the
time of normality appears as illustrated in FIG. 26F. In this case,
the phase is equivalent between the inflection points MP2, MPc, but
the value thereof differs between the inflection points MP2,
MPc.
[0183] Therefore, when the cam switching mode is the third mode,
the inflection point MP2 appears in the locus M, and the inflection
point MP2 is an inflection point at which the deviation T.sub.21 is
smaller than a predetermined value .beta..sub.T and the deviation
P.sub.21 is greater than a predetermined value .beta..sub.P, the
determination unit determines that the switching abnormality is
present. The determination unit also determines that the
abnormality form is the incomplete detachment of the pin Pn21. When
it is duly determined that the abnormality form is the incomplete
detachment of the pin Pn21, the second control unit can perform,
for example, the limiting of the maximum rotation speed of the
internal combustion engine 50 and the limiting of the amount of
fuel injected. The third control unit can perform the decreasing of
the EGR ratio.
[0184] As illustrated in FIGS. 26G and 26H, when the fixation of
the pin Pn21 occurs in the third mode, the exhaust valve 55 is
driven with the cam Cc. As a result, the inflection point MP2 that
does not appear at the time of normality appears as illustrated in
FIG. 26I. In this case, the inflection point MP2 is immovable
before and after the cam switching operation.
[0185] Therefore, when the cam switching mode is the third mode,
the inflection point MP2 appears in the locus M, and the inflection
point MP2 is immovable before and after the use cam is switched in
the third mode, the determination unit determines that the
switching abnormality is present. The determination unit determines
that the abnormality form is the fixation of the pin Pn21. When it
is duly determined that the abnormality form is the fixation of the
pin Pn21, the second control unit can perform, for example, the
limiting of the maximum rotation speed of the internal combustion
engine 50 and the limiting of the amount of fuel injected. The
third control unit can perform the decreasing of the EGR ratio.
Whether the inflection point MP2 is immovable can be determined,
for example, depending on whether the deviation P.sub.22 is smaller
than a predetermined value.
[0186] The determination unit, which determines the abnormality
form as described above when the cam switching mode is the third
mode, determines the abnormality form on the basis of the cam
switching mode and the inflection point MP1 and determines the
abnormality form on the basis of the cam switching mode and the
inflection point MP2 when the cam switching mode is the third
mode.
[0187] The ECU 70 can determine whether the switching abnormality
due to the mechanical failure in the third mode is present by
determining whether the switching abnormality due to the mechanical
failure is present, for example, in the same way as in the first
control example or the second control example in the third mode.
Accordingly, the flowchart illustrating the control operation
example of the ECU 70 is not illustrated.
[0188] FIGS. 27A to 27C are diagrams illustrating first
responsiveness failure. The first responsiveness failure is a
response delay of the switching timing of the use cam occurring
between the coupling mechanisms 631, 632 (the moving timing between
the pins Pn11, Pn21) in the unit U and can occur in the third mode.
FIG. 27A is the same diagram as FIG. 12A and illustrates the first
responsiveness failure. FIG. 27B is the same diagram as FIG. 12B
and illustrates the first responsiveness failure. FIG. 27C is the
same diagram as FIG. 12C and illustrates the first responsiveness
failure.
[0189] Here, in the third mode in which the fluctuation portions
63a, 63b are coupled to each other and the fluctuation portions
63b, 63c are decoupled from each other, the switching of the use
cam in normality is performed as follows. That is, by first causing
the pint Pn21 to decouple the fluctuation portions 63b, 63c from
each other, the use cam is set to the cam Cb. Then, by causing the
pin Pn11 to couple the fluctuation portions 63a, 63b to each other,
the use cam is set to the cam Ca.
[0190] On the other hand, since the response delay occurs in
movement of the pin Pn21 as the first responsiveness failure in the
third mode, a situation in which the pin Pn21 moves later than the
pin Pn11. In this case, by first causing the pin Pn11 to couple the
fluctuation portions 63b, 63c to each other, three fluctuation
portions of the fluctuation portion 63a to the fluctuation portion
63c are coupled to each other as illustrated in FIG. 27A. As a
result, the use cam is set to the cams Ca, Cc. By causing the pin
Pn21 to decouple the fluctuation portions 63b, 63c, the use cam is
set to the cam Ca.
[0191] Therefore, when the first responsiveness failure occurs, the
use cam is temporarily set to the cams Ca, Cc. Whether the cam Ca
is set as the use cam can be determined depending on whether the
inflection point MP1 at which the deviation T.sub.11 is smaller
than a predetermined value .gamma.1 (smaller than or equal to the
predetermined value .gamma.1 herein) appears. Whether the cam Cc is
set as the use cam can be determined depending on whether the
inflection point MP2 appears.
[0192] Accordingly, when the cam switching mode is the third mode,
the inflection points MP1, MP2 appear in the locus M, and the
inflection point MP1 is an inflection point at which the deviation
T.sub.11 is smaller than the predetermined value .gamma.1, the
determination unit determines that the switching abnormality is
present. The determination unit also determines that the
abnormality form is the first responsiveness failure. When it is
duly determined that the abnormality form is the first
responsiveness failure, the second control unit can perform, for
example, the limiting of the maximum rotation speed of the internal
combustion engine 50 and the limiting of the amount of fuel
injected.
[0193] A third control example will be described below with
reference to the flowcharts illustrated in FIGS. 28A to 30. The
third control example is an example of an individual control
operation of causing the ECU 70 to perform an operation of
switching the use cam based on the third mode and to determine
whether the switching abnormality due to the first responsiveness
failure is present in the switching operation. In the third control
example, a part of determining whether the switching abnormality
due to the first responsiveness failure is present is extracted and
described out of the control operation of determining whether the
switching abnormality in the third mode is present. In the
following description, description of the same control operation as
the above-mentioned control operation will not be appropriately
repeated.
[0194] The ECU 70 determines whether a switching request for
switching the use cam from the cams Cb, Cc to the cam Ca is given
(step S301). When the determination result is positive, the ECU 70
turns off the OCV 82 and turns on the OCV 81 through the positive
determination of step S302 and step S303 (step S304). Accordingly,
the operation of switching the use cam based on the third mode is
performed. Subsequently, the ECU 70 performs use cam determinations
A and B (steps S305 and S306).
[0195] Use cam determination A is determination of whether the cam
Ca is set as the use cam. Use cam determination B is determination
of whether the cam Cc is set as the use cam. Use cam determination
A is illustrated as a sub-routine in the flowchart illustrated in
FIG. 29 and use cam determination B is illustrated as a sub-routine
in the flowchart illustrated in FIG. 30.
[0196] In use cam determination A, the ECU 70 calculates the
deviation T.sub.11 (step S321) and determines whether the
calculated deviation T.sub.11 is smaller than or equal to a
predetermined value .gamma.1 (step S322). When the determination
result is positive, a flag C2 is set to ON (step S323). When the
determination result is negative, the flag C2 is set to OFF (step
S324). The flag C2 is a flag indicating that the cam Ca is set as
the use cam. After steps S323 and S324, the sub-routine of use cam
determination A ends.
[0197] In use cam determination B, the ECU 70 calculates the
deviation P22 (step S331) and determines whether the calculated
deviation P.sub.22 is zero (step S332). When the determination
result is positive, a flag C3 is set to ON (step S333). When the
determination result is negative, the flag C3 is set to OFF (step
S334). The flag C3 is a flag indicating that the cam Cc is set as
the use cam. After steps S333 and S334, the sub-routine of use cam
determination B ends.
[0198] After the sub-routine of use cam determination B ends, the
ECU 70 determines whether both the flags C2, C3 are in the ON state
(step S311). When the determination result is positive, the ECU 70
sets a flag C1' to ON (step S312). The flag C1' is a temporary
abnormality flag indicating that it is provisionally determined
that the switching abnormality is present and it is determined that
the abnormality form thereof is the first responsiveness
failure.
[0199] Subsequently, the ECU 70 determines whether the state where
the flag C1' is in the ON state is maintained for a predetermined
time (step S313). When the determination result is negative, the
control process flow returns to step S305. When the determination
result is positive, the flag C1' is set to OFF and a flag C1 is set
to ON (step S314). The flag C1 is a due abnormality flag indicating
that it is duly determined that the switching abnormality is
present and it is determined that the abnormality form thereof is
the first responsiveness failure. In this case, the ECU 70 limits
the maximum rotation speed of the internal combustion engine 50 and
limits the amount of fuel injected (step S315).
[0200] When the determination result of step S311 is negative, the
ECU 70 sets the flag C1' to OFF (step S316). Accordingly, it is
duly determined that the switching abnormality of which the
abnormality form is the first responsiveness failure is not
present. After steps S315 and S316, the control process flow
returns to step S311.
[0201] When determining whether the switching abnormality due to
the responsiveness failure (the first responsiveness failure
herein) is present, the ECU 70 may perform the determination, for
example, as follows. That is, when it is duly determined that the
switching abnormality due to the mechanical failure is not present,
it may be determined whether the switching abnormality due to the
responsiveness failure is present. In this case, for example, when
determining whether the switching abnormality due to the mechanical
failure is present, the ECU 70 can determine whether the switching
abnormality due to the responsiveness failure is present on the
basis of the previously-calculated in-cylinder pressure changing
rate dPc/d.theta..
[0202] The ECU 70 may determine whether the switching abnormality
due to the responsiveness failure is present, for example, as
follows. That is, it may be determined whether the switching
abnormality due to the responsiveness failure is present by
alternately determining whether the switching abnormality due to
the mechanical failure is present for each of the same type of
switching requests in which the cam switching mode is identical
(the third mode herein). In this case, the ECU 70 can determine
whether the switching abnormality due to the responsiveness failure
is present, when it is duly determined that the switching
abnormality due to the mechanical failure is not present at the
time of the same type of switching request previously given.
[0203] FIG. 31 is a diagram illustrating second responsiveness
failure. The second responsiveness failure is a response delay of
the switching timing of the use cam that occurs between the plural
cylinders 51a. FIG. 31 is the same diagram s FIG. 12C and
illustrates the second responsiveness failure. In FIG. 31, the
phases of the loci M are presumed to slide so as to illustrate the
loci M in the cylinders 51a, but the phases of the loci M are the
same.
[0204] When the second responsiveness failure occurs, for example,
one of the value and phase of the inflection point MP1 is much more
different than a predetermined degree between the loci M having the
same engine cycle in one cylinder and the other cylinder out of the
plural cylinders 51a at the time of switching the use cam. For
example, a difference in the presence of the inflection point MP2
is present therebetween.
[0205] Accordingly, when the cam switching mode is the first mode
and the one of value and phase of the inflection point MP1 is much
more different than a predetermined degree between the loci M in
which the cam switching mode is the first mode and which have the
same engine cycle in one cylinder and the other cylinder out of the
plural cylinders 51a, the determination unit determines that the
switching abnormality is present.
[0206] When the cam switching mode is the second mode and the
presence or absence of the inflection point MP2 is different
between the loci M in which the cam switching mode is the second
mode and which have the same engine cycle in one cylinder and the
other cylinder out of the plural cylinders 51a, the determination
unit determines that the switching abnormality is present. When the
cam switching mode is the third mode and one of when one of the
value and the phase of the inflection point MP1 is different more
than a predetermined degree and when the presence or absence of the
inflection point MP2 is different between the loci M in which the
cam switching mode is the third mode and which have the same engine
cycle in one cylinder and the other cylinder out of the plural
cylinders 51a, the determination unit determines that the switching
abnormality is present.
[0207] In this case, the determination unit determines that the
abnormality form is the second responsiveness failure. When it is
duly determined that the abnormality form is the second
responsiveness failure, the second control unit can perform, for
example, the limiting of the maximum engine speed of the internal
combustion engine 50 and the limiting of the amount of fuel
injected.
[0208] A fourth control example will be described below with
reference to the flowcharts illustrated in FIGS. 32 and 33. The
fourth control example is an example of an individual control
operation of causing the ECU 70 to determine whether the switching
abnormality due to the second responsiveness failure is present in
the operation of switching the use cam. In the fourth control
example, the cam switching mode is the first mode. In the following
description, description of the same control operation as the
above-mentioned control operation will not be appropriately
repeated.
[0209] The ECU 70 determines whether a switching request for
switching the use cam from the cam Cb to the cam Ca is given (step
S401). When the determination result is positive, the ECU 70 turns
on the OCV 81 through the positive determination of step S402 and
step S403 (step S404). Accordingly, the operation of switching the
use cam based on the first mode is performed. Subsequently, the ECU
70 performs switching delay cylinder determination (step S405).
[0210] The switching delay cylinder determination is determination
of whether the second responsiveness failure is present. The
switching delay cylinder determination is illustrated as a
sub-routine in the flowchart illustrated in FIG. 33. In the
switching delay cylinder determination, the ECU 70 calculates a
deviation T.sub.i (step S421). The deviation T.sub.i is a deviation
T.sub.11 for each cylinder 51a (#i cylinder) and a deviation
T.sub.11 in each of the loci M having the same engine cycle.
Subsequently, the ECU 70 calculates the average value T.sub.0 of
the deviations T.sub.i (step S422) and sets a cylinder number i to
zero (step S423).
[0211] Subsequently, the ECU 70 determines whether the cylinder
number i is greater than 4 (step S424). When the determination
result is negative, the ECU 70 adds 1 to the cylinder number i
(step S425) and determines whether the magnitude of the difference
between the deviation T.sub.i and the average value T.sub.0 is
greater than a predetermined value .delta. (step S426). When the
determination result is positive, the ECU 70 determines whether a
switching delay is present in the cylinder of #i (step S427). After
the negative determination of step S426 or after step S427, the
control process flow returns to step S424. When the determination
result of step S424 is positive, the sub-routine of the switching
delay cylinder determination ends. Whether a switching delay is
present in the cylinder of #i may be determined using other
methods.
[0212] Subsequently, the ECU 70 determines in which of the plural
cylinders 51a it is determined that the switching delay is present
(step S411). When the determination result is positive, a flag D'
is set to ON (step S412). The flag D' is a temporary abnormality
flag indicating that it is duly determined that the switching
abnormality is present and it is determined that the abnormality
form is the second responsiveness failure.
[0213] Subsequently to step S412, the ECU 70 determines whether the
state where the flag D' is in the ON state is maintained for a
predetermined time (step S413). When the determination result is
negative, the control process flow returns to step S405. When the
determination result of step S413 is positive, the ECU 70 sets the
flag D' to OFF and sets a flag D to ON (step S414). The flag D is a
due abnormality flag indicating that it is duly determined that the
switching abnormality is present and it is determined that the
abnormality form is the second responsiveness failure. In this
case, the ECU 70 limits the maximum rotation speed of the internal
combustion engine 50 and limits the amount of fuel injected (step
S415).
[0214] When the determination result of step S411 is negative, the
ECU 70 sets the flag D' to OFF (step S416). Accordingly, it is duly
determined that the switching abnormality of which the abnormality
form is the second responsiveness failure is not present. After
steps S415 and S416, the control process flow returns to step S411.
In step S415, specifically, the ECU 70 limits the amount of fuel
injected for each cylinder 51a. For example, the ECU 70 may limit
the amount of fuel injected or the EGR ratio in the cylinder 51a in
which it is determined in step S427 that the switching delay is
present while the flag D' is in the ON state.
[0215] Principal operational advantages of the internal combustion
engine 50 will be described below. As described above, an effect of
the mechanical failure or the responsiveness failure is reflected
in the locus M. Such an effect is reflected in the locus M in a
predetermined period K. Accordingly, the internal combustion engine
50 including the ECU 70 as an abnormality determining device that
determines whether the switching abnormality is present on the
basis of the locus M in the predetermined period K can determine
whether the switching abnormality is present.
[0216] Specifically, when the switching of the use cam is normally
performed, the effect of the mechanical failure or the
responsiveness failure is reflects in the locus M obtained in at
least one period of a period in which the exhaust valve 55 is
opened with the switching of the use cam and a period in which the
exhaust valve 55 is not opened with the switching of the use cam.
Accordingly, the internal combustion engine 50 has a specific
configuration in which the ECU 70 further determines whether the
switching abnormality is present with the predetermined period K as
the period on the basis of the cam switching mode, and thus can
determine whether the switching abnormality is present.
[0217] Specifically, the effect of the mechanical failure or the
responsiveness failure is reflected in the predetermined item of
the locus M. Accordingly, the internal combustion engine 50 has a
specific configuration in which the ECU 70 determines whether the
switching abnormality is present on the basis of the predetermined
item of the locus M when determining whether the switching
abnormality is present on the basis of the locus M, and thus can
determine whether the switching abnormality is present.
[0218] Specifically, the effect of the mechanical failure or the
responsiveness failure is reflected in the locus M obtained in the
predetermined period K after the switching of the use cam has
started. Accordingly, the internal combustion engine 50 has a
specific configuration in which the predetermined period K is a
period after the switching of the use cam has started, and thus can
determine whether the switching abnormality is present.
[0219] The internal combustion engine 50 has a specific
configuration in which the ECU 70 as the abnormality determining
device determines that the variable valve mechanism 60 is abnormal
when it is determined that the switching abnormality is present in
at least one of the plural modes and determines that the variable
valve mechanism 60 is normal when it is determined that the
switching abnormality is not present in all of the plural modes,
and thus can appropriately determine whether the abnormality of the
variable valve mechanism 60 is present on the basis of whether the
switching abnormality is present.
[0220] The internal combustion engine 50 has a specific
configuration in which the variable valve mechanism 60 selects a
cam to be used to drive the exhaust valve 55 out of three or more
cams (the cams Ca, Cb, and Cc herein) as the plural cams and
includes plural fluctuation portions (fluctuation portions 63a,
63b, and 63c herein) individually fluctuating in accordance with
the cam profiles of the plural cams and relaying the dynamic power
from the cam shaft 65 to the exhaust valve 55 and plural coupling
mechanisms (the coupling mechanisms 631, 632) performing coupling
or decoupling between two fluctuation portions of the plural
fluctuation portions.
[0221] In this case, for example, in the third mode, the mechanical
failure may occur in the respective coupling mechanisms 631, 632.
For example, the first responsiveness failure or the second
responsiveness failure may occur. That is, the switching
abnormality may occur in various forms. In this case, since it is
preferably determined that the switching abnormality is present,
the internal combustion engine 50 is specifically suitable for this
configuration.
[0222] In the internal combustion engine 50, the plural cams
include the cams Ca, Cb, and Cc, the plural fluctuation portions
include the fluctuation portions 63a, 63b, and 63c, and the plural
coupling mechanisms include the coupling mechanism 631 having the
pin Pn11 and the coupling mechanism 632 having the pint Pn21. The
valve driving portion 62 is disposed in the second fluctuation
portion 63b, the valve opening period of the exhaust valve 55 based
on the cam Cb is included in the valve opening period of the
exhaust valve 55 based on the cam Ca, and the cam profiles of the
cams Ca, Cb are set so that the amount of lift of the exhaust valve
55 is greater with the cam Ca than with the cam Cb. In addition,
the cam profile of the cam Cc is set so as to drive the exhaust
valve 55 at a timing different from that of the cam Ca or the cam
Cb and the plural modes include total six modes (hereinafter,
referred to as a first configuration). That is, the internal
combustion engine 50 can determine whether the switching
abnormality is present, for example, in the first
configuration.
[0223] The internal combustion engine 50 has a specific
configuration (hereinafter, referred to as a second configuration)
in which the ECU 70 determines whether the abnormality of the
coupling or decoupling performed by at least one of the pins Pn11,
Pn21 is present when determining whether the switching abnormality
is present, and thus can determine whether the switching
abnormality is present.
[0224] The mechanical failure or the responsiveness failure can be
identified on the basis of the locus M in the predetermined period
K for each cam switching mode. Accordingly, the internal combustion
engine 50 has a specific configuration in which the ECU 70 as the
abnormality determining device further determines the abnormality
form of the switching abnormality on the basis of the cam switching
mode and the locus M in the predetermined period K, and thus can
cope with situations when the switching of the use cam is not
normally performed.
[0225] In the internal combustion engine 50 having the first
configuration or the second configuration, it is possible to
distinguish the first responsiveness failure, which may occur when
the internal combustion engine 50 has the first configuration or
the second configuration, from other failure and to cope with the
situation. Accordingly, it is possible to cope with a large degree
of disorder such as destruction of the valve system that may occur
by the valve bounce, for example, in a state where three portions
are coupled occurs.
[0226] The internal combustion engine 50 has a specific
configuration in which the ECU 70 determines the abnormality form
on the basis of the cam switching mode and the inflection point MP1
when the cam switching mode is the first mode. Accordingly, the
internal combustion engine 50 can determine the abnormality form of
the mechanical failure occurring in the coupling mechanism 631 at
the time of switching the use cam based on the first mode. In this
case, the internal combustion engine 50 can determine which of the
bounce of the pin Pn11, the oblique insertion of the pin Pn11, and
the fixation of the pin Pn11 the abnormality form is.
[0227] The internal combustion engine 50 has a specific
configuration in which the ECU 70 determines the abnormality form
on the basis of the cam switching mode and the inflection point MP2
when the cam switching mode is the second mode. Accordingly, the
internal combustion engine 50 can determine the abnormality form of
the mechanical failure occurring in the coupling mechanism 632 at
the time of switching the use cam based on the second mode. In this
case, the internal combustion engine 50 can determine which of the
bounce of the pin Pn21, the oblique insertion of the pin Pn21, and
the fixation of the pin Pn21 the abnormality form is.
[0228] The internal combustion engine 50 has a specific
configuration in which the ECU 70 determines the abnormality form
on the basis of the cam switching mode and the inflection point MP1
and determines the abnormality form on the basis of the cam
switching mode and the inflection point MP2 when the cam switching
mode is the third mode. Accordingly, the internal combustion engine
50 can determine the abnormality form of the mechanical failure
occurring in the coupling mechanisms 631, 632 at the time of
switching the use cam based on the third mode. In this case, the
internal combustion engine 50 can determine which of the bounce of
the pin Pn11, the oblique insertion of the pin Pn11, and the
fixation of the pin Pn11 the abnormality form is. The internal
combustion engine can also determine which of the bounce of the pin
Pn21, the incomplete detachment of the pin Pn21, and the fixation
of the pin Pn21 the abnormality form is.
[0229] The internal combustion engine 50 has a specific
configuration in which the ECU 70 determines that the abnormality
form is the first responsiveness failure, when the cam switching
mode is the third mode, the inflection points MP1, MP2 appear in
the locus M, and the inflection point MP1 is an inflection point at
which the deviation T.sub.11 is smaller than a predetermined value
.gamma.1. Accordingly, the internal combustion engine 50 may
determine that the abnormality form is the first responsiveness
failure at the time of switching the use cam based on the third
mode.
[0230] The internal combustion engine 50 has a specific
configuration in which the exhaust valve 55, the cams Ca, Cb, and
Cc, the fluctuation portions 63a, 63b, and 63c, and the coupling
mechanisms 631, 632 are disposed for each cylinder 51a, and the ECU
70 determines that the abnormality form is the second
responsiveness failure as described above. Accordingly, the
internal combustion engine 50 may determine the second
responsiveness failure at the time of switching the use cam based
on the first to third modes.
[0231] The internal combustion engine 50 has a specific
configuration in which the ECU 70 repeatedly determines whether the
switching abnormality is present when determining whether the
switching abnormality is present, and the ECU 70 duly determines
that the switching abnormality is present when it is repeatedly
determined for a predetermined time that the switching abnormality
is present. The ECU 70 is configured to duly determine that the
switching abnormality is not present when it is determined that the
switching abnormality is not present before it is repeatedly
determined for a predetermined time that the switching abnormality
is present. Accordingly, the internal combustion engine 50 may
further identify a case where the switching of the use cam is not
temporarily normally performed and then may cope with the
situations.
[0232] The internal combustion engine 50 has a specific
configuration in which it further includes the ECU 70 as a control
device performing the fail-safe control depending on the
abnormality form determined by the ECU 70 as the abnormality
determining device and in which the fail-safe control includes at
least one of the limiting of the maximum vehicle speed, the
limiting of the maximum rotation speed, and the limiting of the
amount of fuel injected. That is, the internal combustion engine 50
has such a specific configuration and thus can actually cope with
the situations when the switching of the use cam in the variable
valve mechanism 60 is not normally performed. By coping with the
situations, specifically, the internal combustion engine 50 can
prevent or suppress generation of abnormal noise or generation of
vibration or can prevent destruction of the same valve system.
[0233] The internal combustion engine 50 has a specific
configuration in which it further includes the ECU 70 as a warning
device giving a warning when the ECU 70 determines that the
switching abnormality is present, and thus can promote a
countermeasure suitable for this case.
[0234] The internal combustion engine 50 has a specific
configuration in which it further includes the ECU 70 as an EGR
ratio limiting device limiting the EGR ratio depending on the
abnormality form determined by the ECU 70 as the abnormality
determining device, and thus may prevent or suppress degradation of
exhaust emission or degradation of output power when the switching
of the use cam in the variable valve mechanism 60 is not normally
performed.
[0235] The internal combustion engine 50 has a specific
configuration in which the ECU 70 as a control device performs the
fail-safe control when the ECU 70 as the abnormality determining
device duly determines that the switching abnormality is present.
That is, the internal combustion engine 50 further identifying a
case where the switching of the use cam is not temporarily normally
performed and then enabling coping with the situations can suitably
perform the fail-safe control as follows.
[0236] The internal combustion engine 50 has a configuration in
which it further includes the ECU 70 as a re-switching device
re-switching the use cam when the ECU 70 as the abnormality
determining device provisionally determines that the switching
abnormality is present and determines that the abnormality form is
the bounce of the pin Pn11 or the pin Pn21. The internal combustion
engine 50 having this configuration can cope with the case by
re-switching the use cam when the abnormality form is the bounce of
the pin Pn11 or the pin Pn21.
[0237] The internal combustion engine 50 has a specific
configuration in which the ECU 70 as a control device performs the
fail-safe controls having different degrees in the abnormality
forms in which the same type of fail-safe controls are performed
out of the abnormality forms determined by the ECU 70 as the
abnormality determining device, and the internal combustion engine
50 may more appropriately cope with the situations.
[0238] The embodiments of the present invention have been described
above in detail. The present invention is not limited to the
specific embodiments but can be modified and changed in various
forms without departing from the gist of the present invention
described in the appended claims.
[0239] For example, the internal combustion engine may be a
single-cylinder internal combustion engine or a spark-ignition
internal combustion engine. For example, in an internal combustion
engine having plural cylinders, the plural cams may be used to
drive the exhaust valve 55 in at least one of the plural cylinders
or the variable valve mechanism may select the use cam to be used
to drive the exhaust valve out of the plural cams in at least one
of the plural cylinders.
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